TM 11-5805-715-34/EE119-DB-MMI-010/E154 CV3478/TO 31W2-2TTC39-12
d. Dial Pulsing from NA TO (Transmit Path).
2-10. Call Processing
The NIU receives a signal on J1-76 (card NIU-B2)
for dial pulse reception from foreign NATO. The
The following paragraphs define the operational re-
signal is inverted by U16 and the output (OFF-
quirements for processing calls through the NIU.
HOOK or ON-HOOK) applied to one-shot U15.
a. Low-Level 2600 Hz Input (ON-HOOK). A
When the SYX signal line goes high (O volts),
low- level 2600 Hz signal is input at amplifier U1 on
transmit controller U12 inhibits high-level 2600 Hz.
receive circuit card NIU-A. The gain of amplifier
When the SYX signal goes low (-26 volts), transmit
U1 adjusts the overall sensitivity of the receive
controller U12 enables high-level 2600 Hz. An ON-
path. The amplifier output is routed through high-
HOOK or OFF-HOOK signal is then amplified by
pass filter U2 to gain adjust amplifier U3 and to
U14 and applied to the circuit switch.
limiter Q1, U9A. The limiter outputs a square wave
e. Release (ON-HOOK). The input received
replica of the analog signal to amplifier U11, which
is high-level (2600 Hz) for greater than 260 msec,
converts the uncontrolled amplitude of the limiter
followed by low-level 2600 Hz.
out- put to the very precisely controlled amplitude
(receive card NIU-A) output goes high and signal
required for input into bandpass filter FLIB. The
processor U6A times the presence of high-level
out- put of the filter is detected by comparator U9B
2600 Hz tone. Analog gate U6B is switched off and
which triggers one-shot U4. When triggered, the
U6C is switched on. Analog gate U6D is switched
output of U4 goes to the true state (high), reporting
off and U6E is switched on. When timeout for re-
the presence of valid 2600 Hz tone to signal
lease is satisfied, J1-32 of card NIU-A goes high
Under control of the signal
and J1-42 of card NIU-B goes low, indicating ON-
processor, band elimination filter FLIA (centered at
2600 Hz) is switched into the voice path through
analog gate U6E, and the SEIZE line at J1-32
(NIU-A) goes high. This level is applied to the
integrator circuit (U1, U7, U8) on transmit circuit
There are no direct control lines to the NIU. Super-
card NIU-B2 which, after the required timeout,
vision is provided indirectly by program (software)
causes signal line SXY (J1-42) to go low (Q2 off).
control of the SF adapters, located in the circuit
b. No Low-Level 2600 Hz Input (OFF-
switch, which, through the presence or absence of
HOOK). The absence of low-level (2600 Hz)
2600 Hz signaling tone, exerts control over the
switches analog gates U6B on and U6C off on
The following paragraphs define the
command from signal processor U6A. The NATO
processing required to effect proper operation of
switch is anticipating receipt of either dial digit or
release (high-level 2600 Hz) for a period of time.
a. Incoming Seizure from Foreign NIU.
Detector output U4 goes low. Output J 1-32 of
(1) The foreign NIU sends SEIZE on SYX
NIU-A goes low and J 1-42 of NIU-B2 goes high
to the local NIU.
(Q2 on). Signal processor U6A switches U6D on
(2) The local NIU sends SEIZE (absence
and U6E off.
of low-level 2600 Hz) on the transmit pair
c. Dial Pulsing from Circuit Switch. When
to the associated SF adapter in the circuit
the input signal is high level and less than release
time, U6B remains on and U6C remains off (high-
(3) SEIZE is detected by the dc scanner
level detection). Detector output U4 goes high and
serving the SF adapter and the CPU is
J 1-32 is high. Analog gate U6D is switched off and
U6E is switched on. When the input has no signal
(4) The CPU waits approximately 1200
(no 2600 Hz), detector output U4 and J1-32 go low.
msec and then returns OFF-HOOK
Analog gate U6E is switched off and U6D is
command (SEIZE ACKNOWLEDGE) to
the SF adapter.
(5) The SF adapter sends SEIZE
ACKNOWLEDGE (absence of low-level
2600 Hz) to the NIU receive pair.
(6) The local NIU returns SEIZE
ACKNOWLEDGE on SXY to the foreign