TA-312 Field Phone
Special Forces SOG at FOB-3, Khe Sanh, had a TA-312 at each fighting position so contact could be made to the Medical Bunker and Operations. When the shelling started the phones would start ringing. This meant someone had been hit.
The TA-312/PT is a two wire, battery-operated field telephone. It may be used in a point-to-point wire system or in any two-wire ring- down subscriber position of a telephone
communications system. The Handset H-60 contains
a push-to-talk switch which connects power for talking.