TM 11-5805-715-34/EE119-DB-MMI-010/E154 CV3478/TO 31W2-2TTC39-12
The NIU contains eight identical channels. Each
dBm 1.5 db for 500 msec., or until OFF-HOOK is
received, whichever comes first. If OFF-HOOK has
channel is interfaced with a single frequency (SF)
not been received when the time-out occurs, the
adapter channel in the AN/TTC-39 and operates in
2600 Hz tone will continue to be sent at -22 dbm
the transmit and receive modes. Two printed circuit
1.5 db (low level) until OFF-HOOK is received. The
cards are used per channel; one for receive (NIU-
2600 Hz tone is routed to the transmit control logic
A) and one for transmit (NIU-B2). A common
by toggle switch S1. This switch is mounted on the
equipment circuit card (NIU-CE) (common to all
transmit circuit card and, when closed, connects
channels) provides the 2600 Hz signal frequency,
the tone from the common equipment circuit card
the 1050 Hz test frequency and the 512 kHz timing
(NIU-CE) to transmit controller U12. With S1 in the
open position, the transmit channel is held in the
SEIZE state for test purposes.
2-3. Transmit Path
(fig. FO-2)
Voice traffic in the transmit direction is routed to
The transmit input from the foreign NIU is applied
sum amplifier U13 in lone V YX. This amplifier also
on circuit card NIU-B2 (fig. FO-3). The transmit
accepts 2600 Hz signaling from the transmit control
control logic receives commands from the foreign
logic. The output of U13 is applied to transmit ad-
NIU over signal line SYX. The state of this line is
just amplifier U14 via R21 which provides variable
sensed by inverter amplifier U16 at the transmit
gain to compensate for line losses between the NIU
path input. This line will be in one of two conditions
and the circuit switch. Test points J2 and J3 at the
as follows:
output of transmit adjust amplifier U14 allow the
signal level to be monitored. A 1050 Hz test tone,
SYX
Command
generated on the common equipment card and
applied to sum amplifier U13 via toggle switch S2,
< 4 mA
ON-HOOK
facilitates the line loss compensation adjustment.
When power is first applied to the NIU, the power
< 4 mA
OFF-HOOK
on clear circuitry consisting of Q1, U4 and U6
applies a signal to the transmit control logic (U12)
The voltage is referenced to the common wire
which ensures that the transmit path is in the ON-
between the two NIU's. Upon receipt of ON-HOOK,
HOOK low-level state.
the transmit control logic will enable the
transmission of 2600 Hz tone to the circuit switch
Hz tone is transmitted at a level of -10
2-3