Daughter Board No. 4 Assembly 1A13A4 Circuit Functioning

TM 11-820-695-35

kHz test signal is not applied to Handset H-156/U.

R20 couples the output signal to the remote signal/alarm

Resistor R14 matches the output impedance of the

circuits.

amplifier to the filter circuit. Resistors R15-R17 form an

impedance matching network in the output of filter FL1.

d. Filtering Components. Capacitors C9 and C10

The output of amplifier A2 is also applied to the speaker

are filter components for the power supply circuits.

amplifier circuit through resistor R18 and pin 12 and to

the 1.6 kHz monitor through resistor R20.

2-54. Daughter Board No. 4 Assembly 1A13A4

Circuit Functioning (fig. 5-43)

b. 1.6 kHz Monitor Circuit. The 1.6 kHz monitor

Daughter board No. 4 assembly 1A13A4 contains

circuit detects the orderwire amplifier 6 input (1.6 kHz

amplifier circuits and the 1.6 kHz monitor circuit. Each

ringing signal). The circuit is comprised of tuned circuit

circuit is described in the following paragraphs.

Z1, amplifiers AS and A4, a level discriminator circuit,

and relay K1. When the 1.6 kHz ringing signal is

NOTE.

detected, relay K1 becomes energized causing the 1.6

kHz ringing signal to be applied to the speaker volume

Amplifiers A1 and A2 are type

control circuit No. 1 through pin 13. Also, the RING

MC1533G integrated circuits and

indicator on the meter panel assembly 1A15A8 changes

amplifiers A3 and A4 are type CA3035

from green to amber.

integrated circuits. A circuit diagram

for each of these circuits is provided

(1) A 1.6 kHz signal at the output of amplifier

in figure 5-24.

A2 is passed by means of voltage dividing resistors R20

through R25, through the 1.6 kHz tuned circuit, and

a. Amplifier Circuits. Amplifiers A1 and A2 amplify

capacitor 016 to amplifier AB. A3 is comprised of three

signals for application to the speaker amplifier 6 monitor

amplifier stages. Pin 1 is the input and pin 3 is the

circuit, and orderwire amplifier 4 monitor circuit.

output of the first stage of AG. The first stage is a

Through orderwire receive oz 4.02 kHz test signals are

frequency reject circuit in that a level will appear at pin 3

applied to the inverting input (pin 1) of amplifier All (ow

only when a 1.6 kHz signal is present. R27 provides

ampl 4). The through orderwire receive signal is applied

negative feedback for gain stabilization. Pin 3 is

through pins 6 and H, transformer T1, resistors R13, R7,

connected to the input (pin 4) of the second stage

and R1 and capacitor C1. The 4.02 kHz test signal is

through resistor R26 and capacitor C15. The output of

applied through pin F, resistors R7 and R1, and

the second stage is pin 5. (The third stage of amplifier

capacitor C1.

The orderwire amplifier inputs, are

A3 is not used.) The output of the first and second

applied to the noninverting input (pin 2) of amplifier A1

stages are coupled to the level discriminator circuit

through pin M and capacitor C2. The amplifier provides

(diodes CR1 through CR5 and resistor R28) through

a gain of approximately 100. Circuit operation and

capacitor C17 and C18.

component function is the same as described in

paragraph 2-53 for amplifier A1 on 1A13A3. The output

(2) The output of the level discriminator

(pin 5) of amplifier A1 is coupled through capacitor C8

circuit is applied to the input (pin 1) of amplifier A4

and resistor R5, appears across potentiometer R6, and

through filter network R29, R30, and C19. Amplifier A4

is applied through pin 1 to orderwire amplifier No. 2.

is the same type of circuit as amplifier A3; however, the

The output of A1 is also applied to the inverting input

third stage of A4 is used (input-pin 6, output-pin 7).

(pin 1)of amplifier A2 through coupling capacitor C9.

Resistors R32 and R31 are input resistors for the second

Also the 4.02 kHz test signal is applied to the inverting

and third stages. When no signal or a signal other than

input of A2 through pin E, resistors R6 and R9, and

1.6 kHz 40 Hz is applied to amplifier 3, the amplitude-

capacitor C9. The orderwire amplifier 6 remote input

phase detector circuit causes the output of A4 to be high

signals are applied to the noninverting input (across

(+12v). For this condition, relay K1 is deenergized.

R10) of amplifier A2 through pin N and coupling

When the ringing signal (1.6 KHz 40 Hz) is applied to

capacitor C10. Amplifier A2 provides a gain of 100 and

amplifier A3, the level discriminator causes the output of

operates the same as amplifier 1A13A3A1 (para 253).

A4 to be low (0 volt). For this condition, relay K1 is

The output of amplifier A2 is coupled through capacitor

energized causing the RING indicator on the meter

C14 and 3 kHz low pass filter FL1 to Handset H-156/U

panel

assembly

1A15A8

by the handset rev -terminal (pin L) Filter FL1 sharply

attenuates signals above 3 kHz, consequently, the 4.02

2-92