TA-312 Phone

© Brooke Clarke, N6GCE

TA-312 with Controls
                    Labeled
TA-312 & TA-955
                    Touch Tone Pad
TA-312 & Off
                    Hook LED
TA-312 with
Labeled Controls
TA-312 &
TA-955 Touch Tone Pad
TA-3212 &
Off Hook LED
TA-312 in Wall Bracket On Hook
TA-312 Wall Bracket Off Hook

Wall Bracket On Hook
Wall Bracket Off Hook


Background

The TA-312 was a successor to the EE-8 field phone used all through W.W.II and will inter operate with the EE-8, being an analog 2 wire system.  This is one of those Army products that's made to be indestructible and last forever like the PRC-90 & URC-10 survival radios.

The TA-312 was used from the 1950s through the 1980s. Replaced by the TA-838 which is the current (2003) analog field phone.

These have been available surplus since late 1960.  It uses 2 each BA-30 ("D") batteries when in the Local Battery (LB) mode.  There is a canvas case with a shoulder strap that can also be used to hang the phone.

It can also be connected to the Plain Old Telephone System, as a receive only extension in stock form, or when the optional TA-955 Touch Tone pad is installed as a fully functioning phone.

Setup for use on POTS

 When the TA-955 Touch Tone adapter is used with the TA-312/PT the mode switch should be set for Common Battery (CB) operation and the INT-EXT switch must be set to INT so as to use the built in H-60/PT handset.  The U-79/U connector for an external H-144(*)/U handset is used for the TA-955. The TA-312 will work on the public Plain Old Telephone System (POTS) when the TA-955 is installed and configured as described above. 

Without the TA-955 the TA-312 can be used as an answer only extension, like in the garage or outside where it needs to be sheltered from the rain.

Off Hook LED

This is a warning that the handset is not "on hook".   Warning people nearby that the phone is live and anything they say can be heard along the line.
In TM 11-5805-201-12 w/change 6, 1 Sep. 1986 Figure 2-3 shows the installation of off hook lamp assembly.  The one shown has the lamp mounted on the end of the phone near the line 2 wire binding posts.  The off hook LEDs that I got from Mike Murphy are clear plastic blocks, about 0.9" long x 0.3" wide x 0.45" high with two lugs that fit under the two BAT screws.  The one in the manual has two wires running to the two BAT screws.

The voltage on the two BAT screws is about 2.5 when the hook switch is down and raises to about 3.2 volts when the phone is off hook.  The lamp assembly has two LEDs (either both Red or both Green) so that it will work when connected to the two screws either way.  One of the LEDs shines brightly when using local "D" cells but only dimly when no batteries are used and the phone is connected to the POTS.

Remove Batteries

When finished using the TA-312 ,or any device that uses batteries, REMOVE BATTERIES.  Other wise the battery will go bad inside the phone and cause acid damage.

Manuals

TM 11-5805-201-12 Operator and Organizational Maintenance Manual
TO 31W1-2PT-291 is the same manual for the Air Force
TM 11-5805-201-20P Organizational Maintenance Repair Parts and Special Tools List for Telephone Set TA-312/PT (NSN 5805-00-543-0012)
TM 11-2300-369-15-1 is on line.
GTA 11-4-17 - Field Telephone TA-312/PT - Local Battery Operation
PS magazine 50th anniversary issue on the work horse TA-312 - remove cover if it gets wet and dry off phone and battery compartment.

Omaha's Surplus carries the CY-12778/PT canvas bag as new old stock 

Mike Murphy carries the TA-955 Touch Tone Adapter and the LED off hook indicator

National Stock Numbers 

Item
NSN
TA-312/PT
5805-00-543-0012
TA-312A/PT 5805-01-217-7310
BA-30
6135-00-120-1020
Case & sling
8465-00-269-0682
case screw
5305-00-054-6670
Case screw washer
5330-00-48-1018
Binding post boots
5970-00-869-6263
handset mouthpiece de-ice shield
4130-00-392-7628
handset retaining spring
5805-01-025-8891
Security Lamp
5805-00-782-9210
Warning Label
"Phone is not disconnected unless handset is seated properly"
7690-00-877-6864
Caution Label
"Do not strap push-to-talk switch"
7690-00-877-6865
Lamp Assembly ( LED Off Hook Indicator ) with wires
5805-00-782-9210

Links

Contemporary Commo Equipment -
Olive Drab - TA-312


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[an error occurred while processing this directive] page created 29 June 2003.