The US signal corps field telephones TA-43/PT and TA-312/PT are nearly identical instruments. The only difference being that the TA-312/PT ads a plug which can be used to connect an external head-/chest-set or an external DTMF dialpad. The instruments are of very rugged construction and are splashproof. The instruments include a magneto, a buzzer type ringer and a handset with push to talk button. Operation in local battery (LB) or central battery (CB) mode can be chosen by a screw slit type mode switch. There is also a third mode CBS for mixed operation with local battery talk and common battery signalling.
I could not find any sources regarding the exact history of the devices. Based on publication dates of technical manual it is assumed that the TA-43/PT was developed and introduced in the late 40ies or early fifties and the TA-312/PT shortly after perhaps in the second half of the fifties. The instruments have been used and probably also manufactured world wide up into the eighties, so it is to be assumed that the numbers go into the millions. The US field manual 24-24 from 1994 still mentions both as the only standard analog LB devices. Jane's Military Communications Yearbook from 1984 mentions a TA-312/PT version made in Korea and an US made TA-312/MOD (with an electronic button operated ring generator).
The components part numbers for the essential parts are identical between the two types:
Only the TA-312/PT supports an external DTMF dial pad TA-955/PT (via the port originally foreseen fo an external head-/chest-set). This dial pad requires it's own 6V battery to operate (Type J, 7K67, 4LR61). The TA-955/PT supports the AUTOVON precedence level dialling with the full 4x4 DTMF dial pad including the FO, F, I and P precedence buttons (for the A,B,C,D DTMF tones).
On the left the TA-312/PT, on the right the TA-43/PT.
This diagram is glued to the inside bottom of the TA-43/PT housing.
A better readable diagram can be found in TM-11-337.
The open TA-43/PT.
The open TA-312/PT.
The CU-350/PT network in the TA-43/PT.
The CU-350/PT network in the TA-312/PT.
The buzzer assembly, the shaft of the volume knob mechanic is visible. (TA-43/PT)
The buzzer assembly, the shaft of the volume knob mechanic is visible. (TA-312/PT)
The hook switch (TA-43/PT).
The hook switch (TA-312/PT).
The magneto (TA-43/PT).
The magneto (TA-312/PT).
The transmitter element TA-117/PT from the TA-43/PT, made in 1963 (Northern Electric).
The element is identical in size and form to the civilian Western Electric F1 transmitter element.
The transmitter element TA-117/PT from the TA-312/PT, made in 1973 (Northern Electric).
The receiver element TA-235/PT from the TA-43/PT.
The element is identical in size and form to the civilian Western Electric U1 receiver element.
The receiver element TA-235/PT from the TA-312/PT.
This H-60/PT handset has been MFP treated in 1968.
The mouthpiece cap on the left without and on the right with de-icing screen.
Open battery compartment for 2x 1,5V BA-30 (D-Cell). TA-43/PT.
Open battery compartment for 2x 1,5V BA-30 (D-Cell). TA-312/PT.
TA-43/PT top view.
Buzzer volume "LOW"->"LOUD".
Mode switch "CB"-"LB"-"CBS".
"LB" is the middle/"default" position.
The "Bat." binding posts can be used to connect an external battery.
TA-312/PT top view.
To the right of the volume control there is the "int." - "Ext." switch which chooses between handset or external head-/chest-set.
Between the battery compartment and the line binding posts the connector for the external head-/chest-set (covered by turnable lid).
TA-43/PT bottom view.
The embossed number 55 in the top right may indicate year of make 1955.
TA-312/PT bottom view.
The embossed number 68 in the top right (not legible on this image) may indicate year of make 1968 (which would correspond to the year of MFP treatment of the handset).
TA-43/PT manufacturers label.
TA-312/PT manufacturers label.
TA-43/PT ready to use.
Handset on-hook hold by the bracket on the receiver side.
The receiver side relatively flat construction shall enable the use with helmet on.
TA-43/PT in canvas bag.
TA-43/PT ready for transport.
Partly disassembled TA-955/PT.
Battery and side panel removed.
TA-955/PT assembled ready to mount.
TA-955/PT mounted on TA-312/PT.
TA-955/PT mounted on TA-312/PT with handset on-hook.
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