Daughter Board No. o Assembly 1A13A5 Circuit Functioning

TM 11-820-695-35

characteristic of the linear amplifier.

Above a

to change from green to amber and ringing tone to be

predetermined value the output of the amplifier follows

applied to the speaker. Diode CR6 protects against

the limiting action of the silicon diode. Voltage regulator

transient voltages when relay K1 is deenergized.

VR1 provides a regulated supply voltage for the peak

(3) Capacitors C3 and C4 are used to

limiter circuits. Handset H-156/U orderwire, 1.1 kHz test

decouple the power supply inputs to 1A13A4. Resistor

tone, or the 4 kHz oscillator test signal is applied to

R8 provides the proper output level from A2 for

amplifier A2 (peak limiter A) through capacitor C7 and

monitoring purposes. Resistor R19 couples the 1.6 kHz

resistor network R19 and R24. The proper handset level

tone to the speaker volume control No. 1 when relay K1

is obtained through voltage divider network R16 and

is energized.

R17. Resistors R14 and R15 provide proper input levels

for the 4 kHz and 11 kHz signals. Resistor R23

2-55. Daughter Board No. o Assembly 1A13A5

minimizes input offset voltage and R25 sets the

Circuit Functioning (fig. 5-44)

operating point of amplifier A2 to provide the proper

Daughter board No. 5 assembly contains the 1.6 kHz

peak limiting.

Minimum output offset voltage is

oscillator circuit, peak limiter circuits, and amplifier

obtained with R26. The output of peak limiter A is

circuits. Each circuit is described in the following

coupled through capacitor C6 and resistor R27 to

paragraphs.

potentiometer R28. The remote phone orderwire hybrid

NOTE

input, ring input 1.6 kHz, or the 4 kHz test signal is

applied to amplifier A3 (peak limiter B) through resistor

Amplifiers A1 through A5 and voltage

divider networks R29 through R33. These inputs are

regulator VR1 on board 1A13A5 are

coupled to peak limiter B through capacitor C9 and

integrated circuits: A1 (type U5B

resistors R34 and R37. Operation and component

770231X), A2 and A3 (type CA3001),

function for peak limiter B is identical to that for peak

A4 and A5 (type MC1533G), and VR1

limiter A above. The +6 volts required for the peak

(type MC1560G). A circuit diagram of

limiters is established in VR1 by resistors R35 and R36.

each circuit is provided in figure 5-

Resistor R38 is a current limiting resistor and capacitor

24.

C10 reduces output noise. The 6 volt output of VR1 is

filtered by capacitor C11 and is applied to peak limiters

a. 1.6 kHz Oscillator Circuit. The 1.6 kHz oscillator

A and B through blocking diode CR2. The output of

generates a 1.6 kHz signal which is used for ringing and

peak limiter A appears across potentiometer R28 and is

also for part of the 1.1/1.6 kHz alternating alarm signal.

coupled to amplifier AS (pin 1) through capacitor C13.

The circuit is comprised of transistor circuit Q1, 1.6 kHz

Peak limiter A output is also applied to orderwire

tuned circuit Z1, and amplifier A1 (osc amplifier).

amplifier No. 2 through pin F. The output of peak limiter

Transistor circuit Q1 and 1.6kHz tuned circuit Z1 form a

B appears across potentiometer R43 and is coupled to

modified Colpitts oscillator circuit. The oscillator control

amplifier A5 (pin 2) through capacitor C14 and to

signal is coupled to the emitter of Q1 through diode CR1

orderwire amplifier No. 6 through pin 6. Amplifier AS

and pin C. The oscillator can be turned on by the RING

provides a gain of 100. Operation and component

switch on meter panel assembly 1A15A8, the MODULE

function of amplifier A5 is identical to amplifier

TEST selector switch on 1A13A1 or the central alarm

1A13A3A1 (para 2-53b). The output of amplifier A5

circuits on 1A13A2 The 1.6 KHz oscillator output is

appears across potentiometer R50 and is coupled-to

applied to amplifier A1 via capacitors C1 and C2.

amplifier A4 (pin 1) through capacitor C21 and to

Amplifier A1 is a general purpose operational amplifier

orderwire amplifier No. 3 through orderwire amplifier

which provides minimum distortion and isolates the

No. 5 inputs are supplied to amplifier A4 (pin 2) through

oscillator from the output circuits. The 1.6 kHz oscillator

capacitor C22. Amplifier A4 provides a gain of 100 and

and amplifier circuit and component function is identical

is identical to amplifier A6. The output of A4 is applied

with that of the 4 32 kHz oscillator described in

to the transmitters orderwire circuits (TO RADIO OW)

paragraph 2-51a.

through capacitor C26, impedance matching resistor R6,

3kHz low pass filter FL1, transformer T1, and output

pins 13 and 14. Filter FL1 sharply attenuates signals

b. Peak Limiters and Amplifier Circuits. Linear

above 3kHz; consequently, the 4 kHz test signal is not

amplifiers A2 and A3 are used as peak limiter circuits.

applied

the

transmitter

The purpose of the peak limiter circuits is to prevent the

input signals from exceeding a predetermined level.

Peak limiting is accomplished by utilizing the diode

2-93