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Field Phones-use & diagnosis
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(Note: posted in the "other" place, in case you're feeling a bit of de ja vous.)

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Jumping away from the beans ‘n bullets dialog for a thread or two…this series of posts will discuss how to test, set up & use US surplus field telephones in both point-to-point applications and Public Switched Telephone Networks (PSTN). I’m targeting folks that might want to expand into local communication, prospective field phone users and even people selling surplus phones. Most of the phones I’ve bought weren’t operating correctly, nearly all were advertised as working (or alluded to that effect), or simply didn’t discuss that aspect at all. I’m guessing they didn’t find or know where to look for testing info…because there isn’t much online. So what follows is what I collected from conversations, troubleshooting and plain old experimenting. And as you’ll see, it’s missing a lot. So please…fill in the voids.

It isn’t meant to be the end-all post about wire line communication, so I invite other members to add their insight and experiences to this discussion.

So, why the interest in field phones? For starters, (and in case you just crawled out from under a rock following a 60 year nap) the high ground today is information. Aside from the “mantique” aspect, the applications are limited only by your creativity. In many cases, they can be used as landline phones, but militarized, weatherproof & on steroids. And when used in point-to-point mode, secure. It means running wire, but that also means no carrier…which means nothing for a radio to intercept. Point-to-point applications:
  • Intercom from house to garage, shed, tent, tree-house, hunting blind/tree stand, etc.
  • Communication between campsites or even tents
  • Communication from cabin to shooting range (our application years ago)
  • Temporary communication back to your house (think lemonade stand, yard-sale table or station)
  • Gate phone to house (you have an electronic gate at the end of your driveway? Really?)

Did I mention secure? There. I just did.

Field telephones allow temporary or even permanent telephone communication between two or more distant points. The primary advantage of field telephones is both security and portability.

Before we delve into field telephones, we need a basic understanding of how conventional telephones work. Your landline telephone is officially called the public switched telephone network (PSTN), or sometimes by industry insiders: Plain Old Telephone Service (POTS). It’s been around in one form or another for over 100 years, and many of the terms hark back to those days.

A PSTN or POTS line has two basic modes of operation, “on hook” and “off hook”. In simple terms, off-hook means the telephone is in use. “On hook” means it isn’t in use. In the days of yore, telephone microphones (“transmitters”) were separate from speakers (“receivers”). Telephones had a hook-like hanger for the receiver that would disconnect the call when hung up. Not far away was a box with a crank handle, which was the ring generator.

[Image: 1910_zps0c26a1e2.jpg]
Candlestick style Western-Electric Telephone with separate ringer box, circa 1910 from my parent’s house. In this picture, the receiver hangs on the hook, in “on hook” mode (hence the term, “on hook”, or “hung up”.

Oh, and ever notice how you hear your own voice in the receiver? That’s called “sidetone” audio, and it’ll be an important diagnostic tool later in this article.

Power


The drop-down wire to the telephone runs back to the telephone central office or “CO” for short. Sometimes we refer to the CO as simply “the switch”. Power for the telephone, in the form of direct current, originates from the CO and powers the telephone through the same two wires that carries voice traffic. This is why all older telephones didn’t use batteries.

When the phone is off-hook, line voltage drops from 48 volts DC to about six volts DC. Sound (audio) becomes low voltage (and variable frequency) alternating current inside the telephone. When sound passes to or from the telephone, the audio (AC signal) rides on top of the DC voltage back to the switch. The switch passes this on to the other end of the path, where the other telephone strips off the six volts DC and passes the audio signal to the receiver. This configuration, in which the telephone is powered from the switch, is called common battery.


[Image: DC_volts_zps937b109e.gif]
Direct current with respect to time. Note that it’s fairly constant. This is the type of power from batteries.




[Image: ac_volts_zps592d4548.gif]
This is alternating current (AC) with respect to time. Note how it ramp up to a peak value, then decays down, reverses polarity and again peaks. The shape of this wave is a sine wave, and is typical of residential AC.



[Image: ACDC_zps13ed9fe2.gif]
Alternating current “floating” on a DC component. AC is solid line, DC is dashed line. Note how AC component never touches or crosses zero.


Also another important detail: Common & Local battery modes of operation. Most field telephones have a selection for “common battery” (CB) and “local battery” (LB). This configures the telephone to pull power from an internal battery, or to look for power on the telephone wire (like the PSTN). For point-to-point, the power source is almost always the batteries in the telephone, so it’s set to Local Battery (LB). If this is set incorrectly, the telephone won’t operate properly, or not at all.


Signaling & switching

Signaling (in the landline context) is the process of alerting the opposite end that a call is waiting for an answer. Landline phones accomplish this by injecting about 100 volts AC at 20 cycles per second into the circuit. The CO or switch looks at the line voltage first. If it sees 48 volts (on-hook), it assumes the ringer circuit’s connected and hits it with 100 volts AC. If the line voltage is six volts, it assumes someone’s on the line and doesn’t inject ringer voltage. The voice circuit will only respond to AC frequencies between roughly 300-3000 cycles per second, so the audio circuits won’t see this high voltage.

[Image: GN-38_front_zps77f010c4.jpg]
Early GN-38 ring generator from an EE-8 field telephone. Crank handle is lightly spring-loaded inward as shown.

[Image: GN-38_rear_zpsd068be21.jpg]
Rear view: GN-38. Lower two terminals deliver about 100 volts AC when crank is turned.


The process of telephones gets more complicated when we add a third or more telephones, and we don’t want to talk to all of them at once. Logically, we want the ability to connect to just the desired telephone and nothing else. The simplest method is a two-pole electrical switch, usually in the form of a patch-cord. Until the advent of electrical switching systems, this was done with a person at a desk that physically plugged telephone connections together (operator). If you’ve watched any older movies, you’ve seen operator-assisted calls.

[Image: UNESCOSwitchboard1_zps8d991a26.jpg]
Operators at a switch. Image: internet source.

Having a live person with the ability to break the circuit, and even listen in was a frequent conversational topic. And in later years, criticism. Lily Tomlin frequently lampooned telcos in her “Ernestine” skits.

And if you’re old enough to remember the TV show Laugh-In, you probably saw Ernestine the Operator (watch her at http://tinyurl.com/5xcro4 and http://tinyurl.com/pjl2xve).

[Image: Lily_Tomlin_operator_zpsf5776c85.gif]
Lily Tomlin portrays Ernestine the Operator

The first generation of automatic switches was pulse (or rotary dialed) systems. These shorted the telephone wires at a preset rate or frequency, which the CO or switch interpreted as connection sequence programming instructions. The pulses would control circuit switches that interconnected the telephone call to the desired station. This was the first form of telephone communication that didn’t require an operator.

[Image: 500.gif]
Western Electric model 500 rotary phone. This was a very popular rotary desk phone, many examples are still in use.

The next generation was done with sound. The sound was pairs of tones at precise frequencies, which was easier to amplify over long distance. Seven tones were used, and they were always mixed to avoid unintentional signaling. These mixed tones are called dual tone multi frequency, or DTMF. It’s also sometimes called “touch tone”. The big plus to DTMF is long distance direct dialing, sans operator. No more Ernestine. Sorry, Lily.
Another plus is DTMF doesn’t require a telephone interface – it’s in the audio frequency range, and an ordinary acoustic link is enough for DTMF signaling. This will be very important later in this article.
Details- http://en.wikipedia.org/wiki/Dual-tone_m..._signaling
http://www.genave.com/dtmf.htm
Here’s a decent article that discusses wireline telephone operation:
PSTN article-http://electronics.howstuffworks.com/telephone-country-codes1.htm

Next post, the “double E-eight” (EE-8).
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#2
EE-8
The EE-8 is the primary field telephone the U.S. used in W.W.II, Korea and saw use with our allies (think Russia & lend-lease). They’re also the most commonly encountered phone on eBay, surplus sources and elsewhere.

The EE-8 wasn’t our first field phone, but it was (and still is) a damn good one. It replaced the EE-3 & EE-5 telephones. The EE-8 can be described as a complete early telephone set in a satchel, including the ring generator.

Parts abound on the internet, one source (phonesurplus.com) will repair & return your EE-8 fully operational. The EE-8 does not contain any active components or semiconductors (read: transistors, vacuum tubes, etc), all components are passive devices. This might be something to bear in mind for persons concerned about EMI/EMP issues. EE-8 phones are tough as concrete rubble, and that’s probably why most EE-8s are still working today.

W.W.II era EE-8s (EE-8-A) had a leather case, the post-war EE-8s (EE-8-B) used heavy canvas. EE-8-B models seem to be more common.


[Image: cd-ee8b-01b.gif]
EE-8 field telephone

Point-to-point operation

Set up & use is dirt-simple. Put two “D” cell batteries in both sets, set to Local Battery (LB) mode, connect the two wires on the binding posts between the phones and crank to ring the other phone. Avoid touching L1 or L2 terminals when cranking, or you’ll ring with the other phone. If you forget, it will remind you. Abruptly. And just because you can doesn’t mean you should. Don’t connect this to younger brother’s bedframe, or little sis’ fish tank frame. Extracting worms from the soil for fishing….ok, maybe.

[Image: EE8_03_zpsce24ecd4.jpg]
Top view of the connections and controls on an EE-8. This EE-8 has the handset wired direct to the telephone, the most common configuration. The two lower posts on the right are line binding posts marked L1 and L2, the top (smaller) post is a negative connection for external power in LB mode. NOTE: line binding posts are not polarity sensitive in CB mode.


[Image: EE8_04_zpsd4bff39c.jpg]
Two D cells in an EE-8. Note how the positive terminals both face upward.


[Image: EE8_05-CB-LB_switch_zpsf9f2b267.jpg]
Common Battery/Local Battery (CB/LB) screw switch on an EE-8. The cutout for the screw is actually the hook switch for CB mode. Resting the phone in the teaspoon shaped depression breaks the audio circuit like a residential telephone.


[Image: EE8_06_zpsd265e89b.jpg]
External power applied to an EE-8. Red jumper is +3 volts DC, black jumper (on BAT -, above L2 binding post) is return.



PSTN operation
The EE-8 will work on modern PSTN telephone systems, with a few caveats. First, set it to Common Battery (CB) mode. Connect the telephone line to terminals L1 and L2. It will receive calls but won’t transmit audio. To transmit audio, you'll need 3 volts to power the transmitter. Either install two D cell batteries or connect a 3 volt DC power source to the +BAT and –BAT terminals. Watch polarity, verify with a voltmeter or multimeter if uncertain. You can make a 3 volt power supply too, see the section titled “LM317 External power supply”. The DC voltage tolerance will be determined by the LM317T, which is usually about 30-35 volts DC. This mean you can safely power it with a 12 or 24 volt automotive battery. You’ll also need to remember to hold the transmit switch on the handset, or the other end won’t hear you. You’ll know this happening when the sidetone audio is gone (sidetone=your own voice appearing in the receiver, gives you an idea what you sound like on the other end). To dial out, you’ll need a DTMF tone dialer. This is a battery-powered hand-held device that produces the DTMF audio tones used for signaling. To dial a call, place the tone dialer over the microphone and press the desired buttons.

[Image: EE8_07_zps7d920b05.jpg]
EE-8 handset, note transmit butterfly switch in center.


Testing for proper operation:

Signaling-You’ll need four D cell batteries, two EE-8 phones and some type of twin-lead wire (speaker wire, cross-connect wire, even appliance zip cord will do). Set mode switch to LB on both sets, place fresh D cell batteries in both units. Connect wire to binding posts (terminals). Extend crank handle of one unit & turn, ringer on other set should ring. Repeat for opposite unit. Note: avoid touching exposed wire and binding posts, you could sustain a mild shock during ringing. Also note an EE-8 ring generator will easily trigger a neon test lamp for 110 VAC. Connect a neon test lamp across the binding posts, turn the ringing generator crank. The neon lamp should immediately light up & flash in time with generator shaft speed.

Audio-lift both handsets, hold one receiver to your ear and keep transmitter away from your mouth. Speak or whistle into other transmitter while holding transmit butterfly switch, you should hear yourself in the receiver. Switch handsets and repeat. Watch for missing audio in one handset. Swap transmit elements between handsets & repeat test, then receiver elements. Note whether symptom follows receiver element or transmit button. If symptom does not follow a handset component, look for a broken wire in the handset cord.

If you don’t have a second EE-8 telephone available, configure the EE-8 for PSTN operation (details, above). You’ll need cell phone (or second PSTN line on a different number), two D cell batteries and some wire. Connect to a PSTN line, place the handset on the cradle next to the CB/LB mode switch. Call the PSTN telephone number the EE-8 should ring. Pick up the EE-8 handset, turn the transmit switch on the handset. Speak or whistle into the EE-8 transmitter. Listen to the cell phone speaker, you should hear yourself. Keep the cell phone microphone away from your mouth to lessen the chance of mistaking sidetone audio for an operational EE-8 handset.

Next, hold the EE-8 receiver to your ear and keep the transmitter away from your mouth. Speak or whistle into the cell phone, you should hear yourself in the EE-8 receiver. Again, keep the EE-8 transmitter away from your mouth since it makes sidetone audio like modern phones.

Experiment to try: The EE-8 isn’t shy about audio amplification. If the microphone element and batteries are good, connect a digital multimeter to the binding posts. Set it to read AC volts, under 10 volts if it isn’t auto-ranging. Turn the transmit switch on, and whistle into the mic. You should see a volt or two of AC…this is your voice!

What to watch for: corroded or missing battery terminals, worn or broken handset cords (most common failed part on EE-8s), dead transmit or receive elements. All parts are readily available as well as full service, see links below.

I don’t like buying electronics on eBay. As many of you are already aware, it’s asking for trouble. But, they are very easy to find there. Three of four EE-8s I bought on eBay required repair, only one worked as received. “Not tested” seems to be eBay code for “broken, so I’m cutting bait and dumping this for cash”. Upshot: they were very easy to diagnose & repair, all four work now.

I had one apart today to lubricate a squeaking ring generator, so I took a few photos of the interior:

[Image: EE8_10_zps91938eb7.jpg] [Image: EE8_11_zps1216aaee.jpg]
Interior of EE-8. Most are in pristine condition like this one. They’re old-school electromechanical devices, no semiconductors or active components.


Features:
  • Uses two “D” cell batteries-VERY long battery life
  • Has external power connection.
  • No dialing capability, outgoing 100 VAC/20 Hz signaling only
  • Two wire point-to-point system
  • CB or LB operation capable
Summary:
  • Two wire point-to-point, will signal TA-312 phones, probably TA-43 & TP-1s.
  • Has external 3v power connection
  • VERY tough, durable, probably the most EMP resistant of all models
  • Very easy to troubleshoot & repair
  • Largest & heaviest
  • Parts readily available
  • Manuals available
  • DTMF signaling requires an acoustic DTMF dialer
  • Absolute must-have for the W.W.II themed man-cave

[Image: EE8_08_zpsd8e046fd.jpg] [Image: EE8_09_zpsf740912a.jpg]
The EE-8 has the wiring diagram & schematic printed on the sides, it’s also on the internet if lost. The EE-8 can be used out of the case like this for sheltered applications.


[Image: ee8_ad_zps3dd770d5.jpg]
Old magazine ad for surplused EE-8s. Image: internet source.


(thanks to dsk for proofreading & pointing out a technical error)
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#3
Wire & reels

First, a word about safety: long wire runs can act as antennas by picking up stray voltage from power lines, static electricity & lightning. Disconnect before thunderstorms. Use common sense-don’t run wires near power lines and avoid elevated installations unless you’re an experienced climber. If a thunderstorm is approaching, consider disconnecting the phones and relocating the wire away from anything valuable. And do this at the first indication of lightning; I keep an AM radio running for this purpose. It will pick up the static crashes and hour or two before there’s any visible or audible sign of trouble.

The main detail of telephone wire is the conductors are at a consistent spacing through the entire run. This is because telephone wire is transmission line, which means that it must have constant impedance along its entire run to minimize attenuation (loss over distance). You don’t need to be an electrical engineer, what you do need to understand is not to unnecessarily disturb the shape, spacing or configuration of the wire. This includes splices, tight turns and smashing forces. More on transmission line theory for the geeks: (math warning – http://tinyurl.com/c6npvp7, http://tinyurl.com/olxt8ux)

That said, WD-1 wire is cheap & plentiful. CAT-5 cable works nicely, as does appliance zip cord and even speaker wire. Appliance zip cord and speaker wire might be OK for short runs, but neither are 120 Ω (ohm) impedance. For long runs, you’ll need 120 Ω wire, which is telephone wire. CAT5 will very like work as good as WD-1, if not better. CAT5 is made for high data speed (wider bandwidth) than WD-1, so it will carry audio nicely. Unfortunately, CAT5 needs a sheltered location. WD-1A is your best bet: it has several zinc coated strands of steel embedded with the copper, making it very resistant to tension & pulling force failures. It also has UV resistant insulation, so it can be left outdoors for some time without degradation.

CAT-5 works well but can’t withstand the catenary forces of point suspension as well as WD-1 wire. If laid down on a surface or buried, CAT-5 probably be okay. Ditto with appliance cord & cross-connect & speaker wire.

If you’re wiring a pair of TA-838s, you’ll be looking for a four wire (two pair) run. Again, CAT-5 should work, the original stuff Uncle Sam used was WF-16 or WF-16/U wire. It consisted of two pair; one green and one pair brown.


Wiring:

Wiring can be as simple as plain point-to-point, or as fancy as you please. Take a moment to view this wartime training film to see how developed the wiring technology was. Also bear in mind: no active devices, no transistors, no amplifiers…just wire and transformers.

[youtube]H4NDVkjT9mg[/youtube]
W.W.II era training film


Wire management:

You’ll need some means of dispensing & recovering wire, the RL-39 reeling machine works nicely for this. Don’t forget to have at least two reeling machines and one empty reel for line inspection. The RL-39 originally came with two carrying straps, and uses the DR-8 series spools. The primary differences between the DR-8, DR-8-A & DR-8-B are the M-221 connector blocks. The DR-8-A has one block, the –B has two. I haven’t seen a plain W.W.II era DR-8 yet, I assume it lacks a terminal block.

[Image: DR8RL39.jpg]
WD-1A wire on RL-39 reeling machine. Image: internet source.

[Image: CAT5E_on_DR8_reel_zps90c6c619.jpg]
CAT-5E on a DR-8 reel mounted on an RL-39 reeling machine.



[Image: DR8A_reel_zps622fb831.jpg]
DR-8 reel showing hairpin clip. Note paracord sling forming a triangle shaped bale support, allowing RL-39 reeling machine to sit upright on a table & pay out wire. I used bowline loops to prevent slippage. Handy for wiring jobs where the reel’s stationary and wire is drawn out (think alarm & light wiring jobs).

The DR-8 reel or spool is 5/16” square drive. I discovered that Plastruct 90625 square tubing is the same size as the square channel in the DR-8 reel, so it’s possible to make your own spools (my source = http://tinyurl.com/npoac2g). I’ve also successfully adapted plain plastic spools to 5/16” square drive. For now, I’ve been making baby open-frame spools for smaller segments of wire at work.

[Image: Mini_reel_on_RL39_01_zpsf316ab67.jpg]
Variations on a theme: Home-made reel from Plastruct 90625 square tubing.

[Image: Plastruct_90625_zps312a2161.jpg]
Plastruct 3/8 square tubing (90625, Cat No. STFS-12) in the package, consisting of four 12” lengths. Each 12” length makes one of the open-frame mini-reels, see below.

[Image: Mini_reel_in_boxJPG_zpsb6c86427.jpg]
Homemade open-frame mini-reel sized to fit in parts box, ready for small wiring jobs.

[Image: Frankenreel_01_zps6d07411b.jpg]
Frankenreel exhibit #1: A pair of old CDs, some PVC pipe and hotglue. Result: CDs occasionally pop off, allowing wire to slip off core. Not a recommended technique until we find a way to get CDs to stick to PVC or CPVC.

[Image: Frankenreel_02_zpscc06eb63.jpg]
Frankenreel exhibit #2: four strips of Plexiglas glued to existing plastic reel, this actually works.


Reeling machine RL-39 is a must-have along with Reel DR-8. These two allow the user to pay out and retract up to 1600 feet of WD-1A wire. Longer if it’s a smaller diameter wire, such as 28 gauge cross-connect wire.

Most of the reeling machines have a plain cotter pin as a clevis block, the original was a hairpin style hitch pin. I found a suitable replacement on Amazon. Again, my source: http://tinyurl.com/osg4wmz

Wire repair
Repairing wire will be a little more challenging than it might appear on first glance. If the wire is suspended (as in an aerial line), tension must also be taken into account. I haven’t tried plain butt connectors, but they should work if you really smashi-gate ‘em really good. Here’s a couple of techniques the big boys used:

Western Union Splice:
[Image: WesternUnionSplice_zpse5dc7176.gif]
Western Union Splice.

[youtube]Mt_zpGQCM8s[/youtube]
Western Union splice procedure

When done properly, it will be stronger than the host wire, and provide an electrical connection at least as good as wire wrapping. For better results, solder the connection. You’ll probably find a butane powered iron idea for this since a power outlet might not be available.

Butt connection:
The official tool for wire repair is the MK-356/G Wire Splicing Kit, which isn’t easy to find. And almost unobtainable is the Splice (sleeve) Connector (NSN 5940-00-818-1774). The closest substitute I found is 3/16” copper tubing trimmed to the same length as the splice sleeve (source: http://tinyurl.com/owsuu7p).


[Image: 356_Connector_01_zps62bc6b54.jpg]
MK-356/G Wire Splicing Kit, complete

[Image: 356_Connector_02_zpsf9d25889.jpg]
MK-356/G Wire Splicing Kit contents

If you use this option, it might be necessary to double the wire over for an acceptable compression grip.

[Image: 356_Connector_03_zpsc156e61d.jpg]
Copper tube ersatz connector (L) and original splice sleeve 5940-00-818-1774 (R-already crimped)

[Image: 356_Connector_04_zpsd60820a4.jpg]
End view, original splice sleeve 5940-00-818-1774 on right. Note inner layer of compressible plastic.

And for the purists, you’ll also be looking for the CS-34 pouch, TL-13 pliers, and a TL-29 electrician’s knife.

[Image: CS-34_01_zps9afd2309.jpg]
CS-34 tool pouch with contents.

[Image: CS-34_02_zps4c17782f.jpg]
CS-34 tool pouch with TL-13 pliers and TL-29 knife.


LM317 External power supply

An external power supply option worth consideration is the LM317 programmable voltage regulator. It’s a stable DC source up to 1 to 1.5 amps, very easy to set up, and up to 40 volts differential. Also handy to have as a variable power supply, constant current generator and even audio amp.

[Image: Power_supplies_zps7bc54e05.jpg]
Two 317 based power supplies: proto board (R-earliest model), prototype on printed circuit (left). The larger capacitors help stabilize voltage and reduce noise, oscillations. Meter is cheap PM-376 panel meter (source- http://tinyurl.com/lvn9dkr) with a 15k resistor in series for reading 0-15 volts DC.

[Image: LM317_pinout_zps81edabe7.gif]
LM317 TO-220 package pinout

[Image: circuit_zps2fa317b5.gif]
Basic 317 regulator circuit.

Here’s the circuit, I made R1=120 Ω. To set output at 3 volts make R2 somewhere between 150 – 180 ohms. 150 ohms should have an output of 2.8 volts; 180 ohms will be around 3.1 volts. 150 & 180 are standard resistor values. If you need an exact voltage value, you’ll need to add a variable resistor to R2.

[Image: PCB_zps6f0a4842.gif]
If you make printed circuits, here’s the circuit board art. It’s configured for a 2K potentiometer as R2, making it fully adjustable. Component values & location marked on the board.


Purchasing

In general, I recommend avoiding eBay as a source unless you’re patient, fairly good at electrical diagnosis & repair. I suspect Uncle Sam weeded out all the broken field phones, tossed them on a pallet (salted the pile with a few good units, too) and sold them surplus. If so, this would account for the extraordinary high number of defective units I’m seeing. When considering one, always check to make sure they’re explicitly listed as working or operational. And check the refund policy, too. The good news is once they’re fixed, they tend to stay that way.

More information:
TA-312/PT
http://www.prc68.com/I/TA312.shtml
http://olive-drab.com/od_electronics_ta312.php

EE-8
http://olive-drab.com/od_electronics_ee8.php

WD-1 wire
http://www.prc68.com/I/MK356.shtml
http://www.operationeastwind.com/NATO/tr...utWire.pdf

UG-184 glow lamps
http://www.signalcenter.com/commo/ebayli...lamps.html


Parts:
Better sources for parts & info
VTS INDUSTRIAL COMPANY
P. O. Box 429
Salome, AZ 85348-0429
(928) 859-3595 EE-8
http://phonesurplus.com/
(EE-8, EE-91)

Signal Center
www.signalcenter.com/
(TA-312, SB-22/PT Switchboard)

I’ve done repeat business with both sources above; they are helpful, amicable and reliable.

OK, supplies are sporadic and/or requires some digging:
www.murphyjunk.bizland.com/
http://www.fairradio.com/
http://www.oldphoneman.com/OldTelephonePartsForSale.htm


Miscellany (Ads, manuals, ephemera, flotsam
http://www.ima-usa.com/u-s-ww2-army-fiel...-of-2.html
https://www.libertytreecollectors.com/pr...oduct=2513
http://tinyurl.com/k8aenhk
http://tinyurl.com/knxhjdk
http://www.kadiak.org/joe/ee8.htm
http://tinyurl.com/mcmhtbv (TA-312 video)
http://www.personal.psu.edu/wmc12/teleph...A-312.html
http://tinyurl.com/n5lp47r
http://www.youtube.com/watch?v=kd9Ch7HsnVs
http://www.youtube.com/watch?v=wt7Ec9GEakk
http://www.youtube.com/watch?v=N1KSjgJjydA
http://www.youtube.com/watch?v=dN1IVfFQgh4
http://tinyurl.com/pvcsw88
Subject matter expert on questions no one's asking.
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#4
TA-1/PT Field Telephone

I had a chance to operate and repair a few TA-1/PT phones (hereafter referred to as “TA-1” for brevity). I get the impression it’s more of a military grade butt set than a bone fide telephone. First, the obvious: it’s sound-powered and doesn’t use batteries. That’s certainly convenient, but comes at a price – range & audio quality. Most powered field telephones communicate reliably for 10 or more miles, the TA-1 runs out of range at “4 km” (2.5 miles) according to TM 11-5805-243-13. That’s about a quarter or less of the range of a powered field phone. If more range is needed, you’ll be searching for some type of relay station or repeater. In which case, it might be a simpler to switch to a powered phone with more range. Field manual illustrations seem to confirm the TA-1 is more of a butt or test set.
[Image: TA-1_zpsrm4tfqhu.gif]

Point to Point Operation:
Point to point operation is about as simple as possible: connect each phone to the end if a twisted wire pair, squeeze ring generator to signal, remember to depress talk switch when speaking. An interesting feature – the speaker uses the same technology as the microphone, so it’s possible to speak into the receiver, and it will transmit the same as the microphone element. I have tried this, it works. I suspect that this receiver reciprocity function might present a security issue, I haven’t investigated this yet.
Another detail – the TA-1 seems to be simplex operation – only one person can talk & be heard at a time. Also, don’t expect the same audio quality as the TA-43 or 312 or EE-8.
Signaling is the same protocol (high voltage, low frequency AC) as the earlier EE-8s and TA-43/TA-312 telephones, so it will work with them.
Important: modern telephones require decent quality 100-120Ω transmission line to carry the signal with minimum loss. This means use 100-120Ω transmission line for anything other than very short runs. Examples of 100-120Ω transmission line include CAT5 wire, WD-1A/TT field telephone wire and telco cross-connect wire. I can’t recall how many youtube videos state a user can use “any type of wire” to make a field phone work. And, the length of the “anywire circuit” is usually the span of their playpen, bedroom or some other short hop that doesn’t require a telephone.

Testing for operation:
Signaling: connect the phones via a twisted pair. Turn up ring volume. Squeeze the ring switch, the other phone should ring. The visual ring indicator should change from black to black with white segments visible. Pressing the talk switch should immediately reset the visual ring indicator.

Audio: The most obvious test seems to be the least conclusive. Connecting both phones with a short length of wire seems like a good idea, but produced false negative results. My guess is the close proximity of the sound source and receiver (me, whistling in to one phone) while straining to hear it on the other) is just too close together. The best field test I found is wrapping one phone with a rubber band to temporarily hold the transmit switch down, connect it to a longer piece of wire and place it next a radio whose volume is about voice/conversation level. Run the wire long enough to be out of earshot distance, connect the other phone and listen. You should clearly hear the radio in the distant phone, but don’t expect loudspeaker volume levels.

Service & component replacement: Aside from the transmit and receive elements, there aren’t many electrical components that can be replaced without soldering. The most common items to fail are the transmit & receive elements, followed by the handset cord. The transmit & receive elements are easy to replace, just about everything else requires pulling the chassis or more. Fortunately it appears there is a good supply of parts (see sources section, below). In the examples the author repaired, one failure was caused by a defective transmit element, another transmit element was shorting from improper assembly by a previous party. An O-ring had been omitted, causing the transmit element to drop deep enough in the housing to ground out. A third TA-1 required replacement of the visual ring indicator coil, which wasn’t particularly difficult.
Good sources of technical, diagnostic and repair information can be found online, perform an online search for the following manuals:
• TM 11-5805-243-13 (troubleshooting, repair procedures)
• TM 11-5805-243-23P (parts diagrams, NSN numbers)

Features:
• Fully compatible with the TA-43, TA-312, EE-8 series phones
• Sound powered, does not use batteries
• Shorter range than powered field phones
• Adjustable ring volume
• Visual ring indicator (also luminous, AKA “glow-in-the-dark”, but not tritium powered)
• Compact, also has a belt hook.
Summary:
• No batteries
• Shorter range
• More compact
• No DTMF option, aside from commercial external DTMF audio generating devices
• Best suited for short-range hops (under 2 miles)



Parts:
Better sources for parts & info

Signal Center
www.signalcenter.com/
(TA-312, SB-22/PT Switchboard, TA-1 parts, complete RL-39 reeling machines, etc)
I’ve done repeat business with Signal Source; they are helpful, amicable and reliable.

http://radionerds.com/images/2/22/TM_11-5805-243-13.PDF
Subject matter expert on questions no one's asking.
Reply
#5
Adapting plastic reels to the RL-39 reeling machine

Here’s how to make an ordinary plastic spool work with an RL-39, and also have perfect concentric alignment on the first try. It’s also a classic example of a process that takes an hour to describe, and five minutes to perform.
The main advantage of this is the ability to pay out wire, but also reel it back in. For longer and more involved wiring jobs, you’ll be able to recover excess wire paid out very quickly. Also, if you’re using commercial wire for your field phones, you’ll be able to reel it back up in a jiffy. The original DR-8 series military reels are selling for $25+, and north of $15 for shipping. This is a cheaper and more versatile option. After this, maybe you’ll be watching for discarded plastic reels at construction sites!

[Image: img_4968_zpsfs372qne.jpg]
[Image: img_4883_zpsr2z0bp27.jpg]

What you’ll need:
• Calipers or similar measuring device accurate to 0.001”. It must be capable of measuring inside and outside measurements with equal accuracy. Note: all measurements in this article are in inches.
• Square plastic tubing that fits snugly over the RL-39 axle (5/16” square drive), Plastruct 90625 works perfectly for this.
• Glue or plastic solvent. Tenax 7R is very effective for this purpose.
• Razor saw or other saw suitable for cutting plastic, miter guide is very helpful too
• Remember sixth grade geometry & Pythagorean Theorem applied

Procedure:
Carefully measure the diameter of the spool bore. Measure it again for accuracy, this is a critical measurement. We’ll call this number D. Note: D will change to h later in this text.
[Image: circle_zpsnjvhfwo0.png]

Now picture a rectangle inside the circle, sized so that the corners just touch the inside of the circle.
[Image: circlerect_zps8erazwzy.png]
We draw a diagonal line from corner to opposite corner. Important detail: This diagonal line is the same length as D (diameter).
[Image: circlerecthyp_zpstgdpfgmd.png]

Next, we remove the circle and we’re left with the rectangle.
[Image: recthyp_zpsrdwblv4u.png]
Since each side of D is the same (one’s inverted), we remove one side temporarily. We’re left with a right triangle.
[Image: triangle_zps64nvqlqx.png]
Next, we label each side. H is the hypotenuse, which is also the same length as D. S is the measurement across the square tubing flat (see next paragraph), and L isn’t known yet.
[Image: triangle_labeled_zps1fdcdoqb.png]

Add numbers where known. Measure the square tubing across the outside flats (for Plastruct 90625 this will be 0.380”), this is S. The hypotenuse (h) is the same as D above. In this example we’ll use an old Radio Shack plastic solder spool with an inside diameter of 1.025”.
To keep this as tactile as possible, here’s where the triangle fits into the picture-we’ve overlaid it over top of the hub & spokes for illustration:
[Image: spokeshubhyp_zpsvfvjtfeg.png]
We also know the angle formed by the intersection of sides L and S is 90 degrees, which allows us to use simple geometry.
[Image: triangle-w-dims_zpsldqe10wx.png]

Since we know S and h, we can take a shortcut to solve for L by using the Pythagorean Theorem. The basic principle of Pythagoras’ Theorem is the square or area of the hypotenuse is equal to the sum of the square areas of the other sides.
[Image: pyth_zps6zti6pjc.gif]

[Image: formulas_zps0jpwruio.gif]

So L is 0.952” long. Also remember that L (0.952”) consists of two spokes and the hub like this:
[Image: spokeshub_zpsgswm0wgw.png]
The hub is 0.380”, so we subtract the equivalent of the hub side to get 0.572” (0.952”-0.380”=0.572”). Since 0.572” represents the combined length of two spokes, one spoke will be exactly half of the remainder (0.572”). So, 0.286” is the spoke length.
[Image: spokes_zpsk2b6vhnw.png]
All spokes will be the same length. Each side will require four spokes with one hub. So cut eight spokes.
[Image: spokesdims_zpsjfsdqk54.png]
Hub length: The hub should be cut the hub the full length of the spool, plus an extra sixteenth or thereabouts. Any excess can be trimmed or filed down. The hub should be full-length for at least two reasons:
1. It will act as a load-bearing axle for heaver spools
2. It maintains self-alignment when sliding the reel square shaft through the hub.
3. Separate hubs are ok for smaller reels, but installing the RL39 axle can be tricky getting the opposite end aligned on longer spool bores. And, there’s a chance of knocking the opposite hub assembly out if you miss. Don’t ask me how I know this.

Glue the spokes on one end of the hub like this:
[Image: spokeshub_assembled_zpsrsnaaroc.png]
When dry, gently attempt to slide the hub into the spool bore. If you’ve measured accurately and cut the spokes to spec, they should fit in snugly. It should be very close, a trifle too large is better than too small. If necessary, bevel cut a small amount of plastic off the first 1/8” of each spoke. Do this just enough that the assembly will start, but need not completely slide, into the spool bore.
At this time, make note of any holes in the spool core for fishing wire. When you install your spoke assembly, don’t cover these holes.
[Image: IMG_5141_zpssj6gpjwe.jpg]
After the glue or solvent has bonded the spokes, slide the hub and spoke into the reel bore. A small amount of the hub should protrude from the other side. Glue the remaining four spokes into place. Allow ample drying time, especially if the spool will be heavy. Speaking of heavy reels, consider cutting the spokes a little over length and then trimming three sides down to the correct length. The longer side always faces out, and when assembled it forms a flange that helps keep the hub adapter captive. With heavier loads, the square plastic tubing might flex a little, possibly loosening in the spool bore. The flanges will prevent the adapter from falling out. See above image.
Your spool is now fully compatible with the RL-39 reeling machine. It will pay out wire, string, paracord, whatever…but now it can recover or retract it with the reeling machine. This means you can refill it. If you perform remote wiring jobs that involve a lot of hand-carrying, this is a very handy trick for taking smaller portions of wire to a jobsite without hauling a larger, heavier spool.
Getting back to the math…you can also do this much faster in Excel, which handles all the numbers. All you do is the cutting & gluing.
[Image: excel_zpsj6urqrsk.png]
The Pythagorean formula is visible in the formula window. Enter the square stock measurement across the flats in B4 and the spool core opening size (aperture) in A4, the answer in C4 is the spoke length. All measurements are in inches.
Parts:
Better sources for parts & info

Signal Center
www.signalcenter.com/
(TA-312, SB-22/PT Switchboard, TA-1 parts, complete RL-39 reeling machines, etc)
I’ve done repeat business with Signal Source; they are helpful, amicable and reliable.

Plastruct 90625
Ebay - http://tinyurl.com/mstsskr
Amazon - http://tinyurl.com/l2xnlg3
Various hobby suppliers, example - http://tinyurl.com/lvgg3n8


RL-39 reeling machines
Ebay - http://tinyurl.com/lr5fhu3
Signal Center - www.signalcenter.com
Various online sources - http://tinyurl.com/qewe8ae


This concludes the field telephone communication research, no doubt as much was left out as what’s here. I hope this will provide utility for the next camp-out, block party, disaster or emergency drill, paint-ball, retreat, hunting cabin/tree-stand intercom, prepper exercise, re-enactor event, roadside lemonade stand, serious man-cave equippage or other gathering where extended and secure communication is an asset.
Subject matter expert on questions no one's asking.
Reply
#6
PA Rifleman;110625 Wrote:
PSTN operation
The EE-8 will work on modern PSTN telephone systems, with a few caveats. First, set it to Common Battery (CB) mode. Connect +BAT and –BAT to the PSTN telephone line. [b]Watch polarity, verify with a voltmeter or multimeter if uncertain.[/b] It will receive calls but won’t transmit audio. It needs a 3 volt DC source, so install the D cell batteries. You’ll also need to remember to hold the transmit switch on the handset, or the other end won’t hear you. You’ll know this happening when the sidetone audio is gone (sidetone=your own voice appearing in the receiver, gives you an idea what you sound like on the other end). To dial out, you’ll need a DTMF tone dialer. This is a battery-powered hand-held device that produces the DTMF audio tones used for signaling. To dial a call, place the tone dialer over the microphone and press the desired buttons.

Great thread, thank you! This thread are really good, and most aspects are covered. I'm not sure how smart it is to be a newbie here and make corrections, the highlighted text does not give meaning for me.
I have used the EE-8 on regular line as a phone for incoming calls only, and polarity of line does not matter at all, but I have connected the line to the line posts. (As described in the TM-11-333 available online)

Some places the generated voltage from the hand generator are described as 110V, I have problems with getting that on my phones, but close to 90V.

The ringer rings at less than 50V so the rest may compensate for a rather long and bad line.

When using an EE-8 on a regular line the current used by the phone is more than 2.5 regular phones, so it might be a problem on some systems.

The TA-312 and TA-43's are more as a regular phone.

dsk
dsk, proud to be a member of pa2a.org since Feb 2016.
Reply
#7
Field telephones from most countries works well together.

Sound powered phones might transmit to small signals to be heard in older phones. On short lines, it will work pretty well together with many other kinds.

The next will be to look for signal systems, handcranked phones (or same signal by electronics) works together.

Some phones does not send out the handcrank signal, but just a beep, these will sometimes work with the others sometimes not.

UK field telephones will pretty often send the beep signal, but receive both types. If you should use this together with an American TA-312 it will work well, if you leave the TA handset off hook.



dsk
dsk, proud to be a member of pa2a.org since Feb 2016.
Reply
#8
dsk,

You are correct on all points.

dsk;172712 Wrote:
PA Rifleman;110625 Wrote:
PSTN operation
…Connect +BAT and –BAT to the PSTN telephone line. ….

Great thread, thank you! This thread are really good, and most aspects are covered. I'm not sure how smart it is to be a newbie here and make corrections,

I appreciate the feedback. You caught a technical error. I fixed it, thanks for pointing it out.

As part of the correction, I had to break the original post into several sections, so the TA312 and the TA-838 are now further down in this thread. When I originally posted them, they were combined into a single post. It also appears to have exceeded an image count, so the original post couldn't be edited as-is.

dsk;172712 Wrote:I have used the EE-8 on regular line as a phone for incoming calls only, and polarity of line does not matter at all,

This is correct for the audio (line) connections to L1 and L2.

dsk;172712 Wrote:but I have connected the line to the line posts.

Also correct.

dsk;172712 Wrote:(As described in the TM-11-333 available online)

I also attached a copy of TM-11-333 to this post. You should also be able to find it online, I found it at http://tinyurl.com/k8aenhk

dsk;172712 Wrote:Some places the generated voltage from the hand generator are described as 110V, I have problems with getting that on my phones, but close to 90V.

The ringer rings at less than 50V so the rest may compensate for a rather long and bad line.


Your observation is correct. You may have also noticed the ringer voltage is also sensitive to turning speed. As is the frequency (about 20 Hz under average turning speeds). The ringer output is actually a range of voltages, and frequencies. So, it isn’t important to get the ringer generator to produce exactly 110 volts at 20 Hz. So, the important point is make sure the generator will reliably make another phone ring. It isn’t scientific, but it does the job.

dsk;172712 Wrote:When using an EE-8 on a regular line the current used by the phone is more than 2.5 regular phones, so it might be a problem on some systems.


Are you referring to the ringer? The transmitted audio isn’t powered off the telephone network, just the receive and the incoming ring signal.

The unit of measure for the ringer circuit in the US is Ringer Equivalence Number, or REN. Here's a way to track down a phone that's loading your system down:

http://www.naturalhandyman.com/iip/infte...ftel2.html
Subject matter expert on questions no one's asking.
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#9
TA-312
The TA-312 is a more compact field telephone. It has all the features of the EE-8, except slightly more compact, more resistant to the elements and a few more features. Like the EE-8, it uses two “D” cell batteries, 100 volt AC signaling and a two-wire connection. So, EE-8s and TA-312s are fully compatible.

[Image: TA-312_good_01_zpsddca5c37.jpg]
TA-312 field phone

It appears the TA-312 may still be in active military service. A lot of internet articles seem to indicate the TA-312 was replaced by the TA-838 (details on the TA-838 in the next post). I seriously doubt this for several reasons. The TA-838 is larger and appears to be made for a sheltered location. I haven’t seen a carry case for the 838, and the 838 requires a four wire system in point to point mode. This would make a major logistical impact in the field, as it would mean carrying twice as much wire or only having half the range in each wire spool. And last but not least: the TA-838 isn’t waterproof. Repeat: it isn’t waterproof. So, Uncle Sam might have a new toy to replace the TA-312, but I doubt it’s the TA-838…or at least the versions I’ve seen to date.

Point-to-point
Set mode to LB, INT-EXT switch to INT, drop two D cell batteries (polarity: one up, one down), and connect the wires to the binding posts. Crank the ring generator to signal (ring) the other phone. Hold Push-To-Talk switch when you speak.

[Image: ta-312_w_callouts_zps5b0f7a9e.jpg]
TA-312 features & controls (click image to enlarge)
http://i147.photobucket.com/albums/r290/...eb2f15.jpg

[Image: TA-312_broken_03_zps568f3df3.jpg]
Ring generator crank hand (folded-right), ringer speaker (left, inset in case)

PSTN operation
The TA-312 is almost ready to go on the landline. You’ll need a DTMF tone dialer; set it to Common Battery (CB) mode and you’re good to go. Unlike the EE-8, it won’t require batteries. It can get power from the PSTN line. And, the PTT switch is bypassed, so you don’t need to remember that, either. In short, it behaves like a regular telephone. Except dialing. And, by happy coincidence, Uncle Sam made the observation. Device TA-955/PT is the official DTMF adapter for the TA-312 telephone. With this, it becomes a regular touch-tone telephone. Tip: the TA-955 appears regularly on eBay for around $30 as new-old-stock (NOS), a DTMF tone dialer can be had for as low as $15.

[Image: DTMF_TONE_DIALER_00_zps1474b946.jpg]
Two views of a typical Radio Shack DTMF tone generator. I think I paid a whopping 25¢ for this at a local yard sale. Search ebay for tone dialers -> http://tinyurl.com/k6kqmzw

[Image: TA-955_01_zps94a386b3.jpg]
TA-955 DTMF adapter for the TA-312 field phone

[Image: TA-955_02_zpse5d926fe.jpg]
TA-955 installed on the TA-312 phone. Note that it interfaces through headset I/O port on top.

[Image: TA-955_03_zps7054d5f8.jpg]
Side view showing how TA-955 covers ring generator crank handle. Ring generator isn’t necessary when using DTMF signaling.

Testing for proper operation:
Signaling-Set mode switch to LB on both sets, place fresh D cell batteries in both units. INT-EXT switch to INT. Connect wire to binding posts. Extend crank handle of one TA-312 & turn, ringer on other set should ring. Repeat for opposite unit. Note: avoid touching exposed wire and binding posts, you could sustain a mild shock during ringing. Also note a TA-312 ring generator will easily trigger a neon test lamp for 110 VAC. Connect a neon test lamp across the binding posts, turn the ringing generator crank. The neon lamp should immediately light up & flash in time with generator shaft speed.

Audio-lift both handsets, hold one receiver to your ear and keep transmitter away from your mouth. Speak or whistle into other transmitter while holding transmit switch, you should hear yourself in the receiver. Switch handsets and repeat. Watch for missing audio in one handset. Swap transmit elements between handsets & repeat test, then receiver elements. Note whether symptom follows receiver element or transmit button. If symptom does not follow a handset component, look for a broken wire in the handset cord or an internal electrical fault.

If you don’t have a second TA-312 telephone available, configure the TA-312 for PSTN operation (details, above). You’ll need cell phone or a second PSTN line, two D cell batteries and some wire. Connect the TA-312 to a PSTN line; place the TA-312 handset on the cradle. Turn the ring volume knob to maximum volume. Call the PSTN telephone number the TA-312 should ring. Pick up the TA-312 handset. Speak or whistle into the TA-312 transmitter. Listen to the cell phone speaker, you should hear yourself. Keep the cell phone microphone away from your mouth to lessen the chance of mistaking sidetone audio for an operational TA-312 handset.

Next, hold the TA-312 receiver to your ear and keep the transmitter away from your mouth. Speak or whistle into the cell phone, you should hear yourself in the TA-312 receiver. Again, keep the TA-312 transmitter away from your mouth since it makes sidetone audio like modern phones. If you have access to a DTMF tone dialer or a TA-955 & a good “J” cell battery, try calling the cell phone. It should work like a regular touch-tone telephone.

If you don’t have a second phone, try powering the TA-312 up, set to LB mode, squeeze PTT switch. Whistle or speak into the mic, you should hear sidetone. This isn’t an accurate test since even if you hear sidetone, there isn’t any assurance the audio is available at the binding post.

What to watch for: corroded or missing battery terminals, worn or broken handset cords, inoperative ringing generator, broken ring volume control. Most parts are available, see links on final post.

[Image: TA-312_broken_02_zps4da2954a.jpg]
Always ask to see the battery spring terminals. If batteries are left in place & forgotten, they often leak causing terminal corrosion. This one had good terminals.

Both of two TA-312s I bought on eBay required repair. One needed a new generator, the second had multiple major failures. Both were advertised as working. As with the EE-8, “Not tested” seems to be eBay code for “Bid now to make this your problem”. Ditto with “operational”. I have a suspicion Uncle Sam dumped all the broken TA-312’s on a pallet or two and sold them surplus…keeping all the functioning one for himself. I seem to be one of three people in the US fixing a few of them. I’d sure like some company. Upshot: TA-312s aren’t impossible to diagnose & repair.

An observation while repairing one…the TA-312 does have semiconductors. It has a large module-like device inside with a cluster of wires soldered to it, it isn’t a serviceable component. And, there isn’t as much open space inside the TA-312. I don’t have any diagnostic info for this module yet.

[Image: TA-312_broken_01_zpsa86b34ec.jpg]
An “operational” TA-312 from a well-meaning seller. Looks *just* like a working one, too.

[Image: TA312_in_the_bag_01_zps617832ac.jpg]
TA-312 in the carry bag. Note circular cutouts for speaker and generator handle.

[Image: TA312_in_the_bag_02_zps93c03b77.jpg]
TA-312 in carry case, top view.

Features:
  • Uses two “D” cell batteries
  • Has external power connection.
  • Has external audio connection for DTMF pad or external H-144/U headset
  • DTMF keypad accessory (TA-955)
  • Two wire point-to-point system
  • Easier to remove & install in carry case (no screws required like the EE-8)

Accessory item: the TA-955 keypad has extra buttons for Autovon functions. Disregard these, as the Autovon system was used in the 1963-76 period. It was a Cold War era high reliability network that featured cables buried 35+ feet deep and call priority. The buttons are:
  • FO-Flash Override
  • F-Flash
  • I-Immediate
  • P-Priority

[Image: ACCESSORIES_02_zps84e305cc.jpg]
An image I couldn’t find elsewhere: the I/O port opened, a clear view of the INT/EXT switch and a few accessories. Clear plastic device wired to phone is a U-184/GT, a neon lamp encapsulated in plastic. It glows when exposed to ring voltage, acting as a silent ringer. Since they’re modular & stack, they can be used as a primitive switchboard. Blue & yellow device below the UG-184 is an electrician’s neon test lamp, residential AC makes it glow…so does ring voltage, making it a handy generator tester. Bag on left contains replacement binding post covers, a good idea if you prefer to avoid random low level shocks.

Summary:
  • Two wire point-to-point, will signal EE-8 phones.
  • External power connection
  • Repairable, although many components are replacement-only
  • Some parts sources, end-user repairable (soldering skills required for some parts replacement)
  • Manuals available
  • DTMF compatible with TA-955 keypad, or with an acoustic DTMF dialer.

TA-838
[Image: TT-838_quarter_view_zps0f16b4b9.gif]

The TA-838 is the most advanced analog field telephone I’ve encountered to date (and one of the more rarer models). It’s also the most complex to date, as you’ll see. The TA-838 is fully compatible with PSTN DTMF, which means it will work as a regular land-line telephone as-is. It even resembles a pay-phone.

[Image: TT-838_front_view_zps9c3f8a80.gif]

Features:
  • Uses four “C” cell batteries, no external power connection.
  • Integrated DTMF keypad, Autovon keys like the TA-312
  • Four wire point-to-point system
  • No external power terminals
  • Many modes of operation (I’ve only been able to figure out two of them)
  • Adjustable ringer volume & ring light for silent operation
  • Case is entirely plastic
  • True ringdown operation capable

[Image: TA-838_01_zpsaad6a172.jpg]
TA-838/TT, front view

[Image: TA-838_02_zps0cd34348.jpg]
TA-838/TT, side view. Upper hole is speaker, smaller hole is vent in case apparently for pressure equalization…and water entry.

PSTN operation:
Set selector to DC/CB under two-wire mode, connect the PSTN wire to the upper terminals (XMT).

[Image: TA-838_07_zps0414b177.jpg]
Mode switch. Dot in slot indicates setting. This one is set to point-to-point operation, or directly to another TA-838.

[Image: TA-838_08_zpsc6802a06.jpg]
Binding posts (wire terminals). Right pair are transmit (XMT), left pair are receive (RCV), and missing binding post covers.

Testing for proper operation:
Connect to another TA-838. Connect upper two terminals (XMT) to lower two terminals (RCV) on the distant set. Connect lower terminals on first set to upper terminals on distant set (Crossover format). Set both TA-838 sets to “PT-PT” mode, make sure both sets have four “C” cell batteries. Turn ringer volume up on both sets. Make sure ringer silent switch isn’t set to mute (up, I think…).
Signaling-Lift one handset, the other phone should ring. The ring is a steady tone for 2-3 seconds. Repeat test for other set.

Note: When one handset is lifted, the other set should automatically ring. There isn’t any ring generator, and it doesn’t use one. This automatic ring feature is called ringdown, and it’s a fairly rare feature. If you’ve ever wondered why it’s difficult to get two phones to work as intercoms, the missing device is a ringdown box between them.

Audio-lift both handsets, hold one receiver to your ear and keep transmitter away from your mouth. Speak or whistle into other transmitter, you should hear yourself in the receiver. Switch handsets and repeat. Watch for missing audio in one handset. Switch transmit elements between handsets & repeat test, then receiver elements. Note whether symptom follows receiver element or transmit button. If symptom does not follow a handset component, look for a broken wire in the handset cord, or maybe an incorrect mode setting, or one wire not properly seated on a binding post.

If you don’t have a second TA-838 telephone available, configure the TA-838 for PSTN operation (details, above). You’ll need cell phone and some wire. Connect to a PSTN line, place the handset on the cradle & turn the ringer volume up. Call the PSTN telephone number with the cell phone, the TA-838 should ring. Pick up the TA-838 handset. Speak or whistle into the TA-838 transmitter. Listen to the cell phone speaker, you should hear yourself. Keep the cell phone microphone away from your mouth to lessen the chance of mistaking sidetone audio for an operational TA-838 handset.

Next, hold the TA-838 receiver to your ear and keep the transmitter away from your mouth. Speak or whistle into the cell phone, you should hear yourself in the TA-838 receiver. NOTE: this only tests the TX circuit, the RX circuit (lower binding posts marked RCV) require a four wire setup to test.

What to watch for
Corroded or missing battery terminals — The TA-838 doesn’t have an external power connection, so they had batteries in them a lot. This increases the chance you’ll find damaged or destroyed battery terminals. It isn’t impossible to fix, just patience and basic soldering skills. In one case, the terminals were completely gone. I harvested spring terminals from an unused “C” cell battery holder, bent them to match the TAT-838 mounting profile & soldered in place. The terminals on the lid are thick enough that there should be some meat left.

Also, if you’re dealing with corrosion, don’t forget to neutralize the electrolyte residue first, or the corrosion may return. To neutralize electrolyte, get a small amount of baking soda and vinegar. Remove the terminals from the phone or device. Add a small amount of water to moisten the baking soda. Place a very small amount of each on crystallized electrolyte (but not in contact with each other!) and see which one reacts to the electrolyte. The one that reacts is the right one to use. PARENTING TIP: this is great way to resurrect old battery powered toys that were forgotten with batteries, and then “rediscovered”. Naturally, you, as a parent, will be expected to undo all that corrosion and neglect.

Also look for worn or broken handset cords. Parts are unavailable except salvaged from other units. You’ll see a TA-838 here and there on the surplus market. I suspect Uncle Sam harvested all the broken units, tossed them in a triwall box and salted the top of the pile with a few good ones to guarantee a sale.

[Image: TA-838_04_zps315184ed.jpg]
Battery terminals repaired from heavy corrosion. Left terminals are original, right pair were repurposed from a “C” cell battery holder. This is a common repair on the TA-838. Cover terminal strips were cleaned & re-tinned from corrosion also.

[Image: TA-838_03_zps1ea7132c.jpg]
Deteriorated handset cord insulation, another common discovery but not serious. This example is still very serviceable but not watertight. The wires are Tinsel wire, so it will continue to work for quite a while longer.

Why I don’t recommend the TA-838:
The TA-838 is a great phone if you already have two or more that are already working. Buying one without testing will likely result in receiving a broken phone.
  • There doesn’t appear to be any parts or service information for them, anywhere. I’m hoping I’ve missed something, but that’s the apparent situation. In other words, if it’s broken, your only opportunity for parts is replacing it or cannibalizing another unit. And, TA-838s tend to have very high asking prices online.
  • It uses a four-wire setup in point-to-point operation, so you’ll need a four wire run. That means a second run of WD-1 wire, or a spool of WF16 (four conductor) wire. Since spools hold a fixed volume, this translates to a shorter distance per spool or additional spools of wire.
  • Uses a different signaling protocol. All of the TA-838’s I’ve examined don’t generate 100 volts AC for signaling in PT-PT mode, it appears to be a lower voltage and may be audio, 570 Hz ring burst according to one source. As such, they aren’t able to signal the older TA-312 & EE-8 series telephones. A TA-838 will only signal another TA-838 in PT-PT mode.

[Image: TA-838_05_zps021679fc.jpg]
TA-838 porn, part I. In case (left), see battery compartment bottom. The battery terminal board is held in by two nuts. Removing the two nuts allows the entire battery terminal card to pull out, making service or even replacement fairly easy.

[Image: TA-838_06_zps9bc28683.jpg]
More TA-838 naughty bits. If anything here looks familiar from a previous occupation, please PM me.

That’s all I can think of right now, I’ll edit this post if I learn anything new. In the meantime, I hope this is some value to someone out there.

Summary:
  • Four wire point-to-point, won’t signal to older TA-312 & EE-8 phones.
  • Appears TA-838 will only point-to-point with another TA-838.
  • No external power connection, expect battery terminal corrosion
  • Not repairable outside of military repair facilities
  • Few (if any) parts sources
  • Almost no documentation, no troubleshooting info
  • PSTN & DTMF compatible as-is, best use: Man-cave or Cold War themed desk phone.

Untested: EE-3, EE-5, TA-43, all digital models (TA-954, 1042, etc) and all foreign sets. I didn’t test these since I don’t have an example right now, I might test them in the future if I get one or two working examples. If someone has any of the previously mentioned phones available for testing, PM me. If digital, I’ll need to borrow a working pair.

I get the impression:
  • The TA-43 is very similar to the TA-312, but missing a few features (external I/O connection, mostly).
  • The EE-3 & 5 are predecessors to the EE-8, and the only item rarer than an operational EE-3/5 are parts for the same.
Subject matter expert on questions no one's asking.
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#10
PA Rifleman;172910 Wrote:
dsk;172712 Wrote:When using an EE-8 on a regular line the current used by the phone is more than 2.5 regular phones, so it might be a problem on some systems.


Are you referring to the ringer? The transmitted audio isn’t powered off the telephone network, just the receive and the incoming ring signal.

The unit of measure for the ringer circuit in the US is Ringer Equivalence Number, or REN. Here's a way to track down a phone that's loading your system down:

http://www.naturalhandyman.com/iip/infte...ftel2.html

Partly, yes. The load at a ring signal to the EE-8 is devided to a part to the ringer, and another actually going trough the voice path. Together this is draw a quite heavy load from the line. In LB mode, this seems to be no problem at all, but some CB systems might detect the great load as a lift off, and hang up on the line. E.g. I have a 1940-something PAX who sometimes act like that. (usually not, but it is at the limit. With one regular (old) phone extra, I get trouble)

I really have fun of playing with different field telephones, and it seems like most of them works well together. US EE-8 TA-43/PT ex-German FF-33 Swedish Norwegian, and some English field telephones. The work well together all of them. Still the 2 most reliable of all seems to be the German FF-33 and the US EE-8, I actually cant decide which is the best. The EE8 is the most easy to carry, the FF33 is the most easy to use, but have no CB mode.

If we had been closer we should have put up a line between each other. They have not invented adapters for magneto telephones for internet... yet. Big Grin

dsk
dsk, proud to be a member of pa2a.org since Feb 2016.
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