TM 11-5805-424-15/NAVELEX 0967-220-9010/TO 31W2-2G-41
ALARM THRESHOLD control resistor 1A1R11),
ALARM THRESHOLD control resistor 1A1R11.
transistor Q9 of the amplitude detector does not
Resistor R50 is the emitter load resistor for
conduct; therefore, the base of amplifier IN-10 is
transistor Q15.
at -15 volts, cutting off transistor Q14. With
(2)
The level threshold is a degenerative
transistor Q14 cut off, the base of amplifier IN-9
operational amplifier (Q3, Q4, and Q5) with an
is connected to -15 volts, which cuts off
emitter follower (Q6) output. The signals that
transistor Q10 and allows capacitor C9 to
are applied to transistor Q3 are amplified,
charge. Diodes CR9 and CR11 serve as small
inverted, and fed to transistor Q5. Transistor
dropping resistances when transistor Q11 is
Q4 provides degenerative feedback for
forward biased.
transistor Q6. Resistor R11 and capacitor C3
(6) REC CARRIER ALARM TIME control resistor
form a shelf network that allows transistor Q5
1A1R12 adjusts the time required (2 minutes or
sufficient time to change amplification levels
longer) for capacitor C9 to reach a potential
without developing unnecessary phase shifting
sufficiently positive to be passed by diode CR11
between the input and output signals. Resistor
to transistor Q11, causing transistor Q11 to
R13 is the common emitter resistor for
conduct. With transistor Q11 conducting, a
transistors Q3 and Q4, resistors R9 and R10 set
ground is applied to bias transistor Q12 into
the operating bias for transistor Q5, and resistor
conduction, providing +6 volts to activate the
R12 is the collector load resistor for transistor
common alarm circuit.
Q5. Resistors R14 and R16 form a voltage
divider network that limits the amount of
(7) Resistor R35 is the collector load resistor for
degenerative feedback to transistor Q4.
transistor Q11, resistor R36 provides direct
coupling between transistors Q11 and Q12, and
(3)
The output from transistor Q6 is applied through
resistor R37 is the collector load for transistor
coupling capacitor C5 to the base of paraphrase
Q12.
amplifier Q7 in the amplitude detector.
Resistors R19 and R20 provide initial operating
(8) The alarm signal (+6 volts), inverted by
bias for transistor Q7. The amplitude detector
amplifier IN-11, is applied to the external
operates exactly the same as the transmit
receive carrier alarm terminal 14 of terminal
carrier alarm circuits (para 5-136(2)).
board TB1 as a ground (transistor Q13
conducting). If a no-alarm condition exists, the -
(4)
The amplitude detector output is applied through
6 volts at the Q12 collector holds transistor Q13
amplifier IN-10 to amplifier IN-9 and to the
cut off, which provides a positive output that is
common alarm circuits in the input interface and
clamped to +6 volts by diode CR12. Resistor
common alarm module. As long as a carrier
R39 is the collector load resistor for transistor
signal is detected by the amplitude detector,
Q13.
amplifier IN-10 conducts. The current flow
through emitter resistor R45, transistor Q14, and
collector load resistor R42 maintains amplifier
5-15. Talk-Request Detector Timing Circuits
IN-9 in a conducting state, thus preventing
capacitor C9 from charging. Transistor Q11 is
held cut off, thereby cutting off transistor Q12
a. General.
The talk-request detector timing
(+15 volts applied to transistor Q12 base).
circuits include an initial timer that when activated upon
With transistor Q12 cut off, -6 volts is applied to
receipt of a receive carrier alarm times out after
the common alarm circuits, so that the common
approximately 1 second (adjustable by TALK REQUEST
alarm circuit is not activated (para 5-24f).
DELAY control resistor 1A1R9). After timing out, the
initial timer activates the window timer, which times out
(5)
When the receive carrier is lost or falls below a
after
predetermined level (as set by REC CARRIER
5-13
