DNVT

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. It is available in either desk set or field telephone models Field models include:

• TA-954/TT
• TA-1035/U
• TA-1042A/U (with data connector for AN/UXC-7 tactical facsimile machine, AN/UGC-144 communications terminal, etc.)

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 connected to a telephone exchange and configured in common battery (CB) mode, the DNVT receives phantom power from the telephone exchange over the send/receive line pairs. (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:

• 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:

• 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

TTC-39 TRI-TAC family brochure from GTE Sylvania

References

• 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)