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The Digital Nonsecure Voice Terminal (DNVT) is a telephone set which transmits and receives conditioned diphase modulated data at a signaling rate of 16 or 32 kilobits per second (kbps) over a 4-wire interface.[1] It is available in either desk set or field telephone models[2] Field models include:

Pairs of TA-1042A/U DNVTs may be used in local battery (LB) mode as simple field phones, without requiring connection to a telephone exchange. The TA-954/TT, however, must always be connected to a telephone exchange as it does not support direct DNVT-to-DNVT connection. When the TA-1042A/U is operated in local battery mode, a power source of 24-56 VDC must be connected to the PWR binding posts on the right side of the phone, with positive voltage connected to the red post.

When connected to a telephone exchange and configured in common battery (CB) mode, the DNVT receives 24-56 VDC phantom power from the telephone exchange over the send/receive line pairs.[2] Positive voltage is applied to either or both of the red RCV terminals, and negative voltage is applied to either or both of the black XMT terminals.

(TBD: Can the TA-1035/U be operated without connection to an exchange? Can either the TA-954/TT or TA-1035/U be powered in LB mode?)

The DNVT offers the following features:[4]

  • Digital telephone/data set for mobile subscriber equipment (MSE) and TRI-TAC systems.
  • Full duplex voice or data communications.
  • Push-to-talk (PTT) for combat radio net interface.
  • Standard four-wire loop interface.
  • Mean time between failures (MTBF): 150,000 hours.
  • Automatic tracking of 16 or 32 kbps switch loop rate via autobaud feature.

The DNVT has the following specifications:[2][5]

  • Data rates of 16 or 32 kbps synchronous or up to 2400 bits per second asynchronous. (TBD: Does this only apply to the TA-1042A/U?)
  • Loop interface: four-wire line, up to 4km of WF-16/U field wire.
  • Line impedance: 125Ω ±10% resistive.
  • Operating voltage: 24 to 56 volts DC.
  • Audio codec: continuously variable slope delta modulation.
  • Signal format: Conditioned diphase at 16 or 32 kbps.
  • Codeword format: Cyclically permuted 8-bit words.
  • Output level: 3V peak to peak.
  • Input level: between 150 mV and 4V peak to peak.

Related Files

Adobe PDF icon.png TTC-39 TRI-TAC family brochure from GTE Sylvania


  1. FM 3-04.120 ¶2-83.
  2. 2.0 2.1 2.2 Kirsch 1981, p. 1609.
  3. FM 3-04.120 ¶2-84.
  4. FM 3-04.120 ¶2-85.
  5. FM 3-04.120 ¶2-86.


  • Kirsch, Alan L. et. al. (November 1981). "The Digital Nonsecure Voice Terminal", IEEE Transactions on Communications, Vol. COM-29, No. 11, pp. 1609-1614. (link)
  • Headquarters, Department of the Army (February 2007). "Air Traffic Services Operations", Field Manual FM 3-04.120 (FM 1-120). (link)