AF Amplifier 1A12A6 - TM-11-5820-695-350082

TM 11-5820-695-35

components, and applied to emitter follower buffer

if the pcm components of the input signals are equal.

amplifier Q5.

The circuits of 1A12A7 (other than the subtractor and

the audio output amplifier) are used to create this

(3) The pcm signal is then applied to the

equality of pcm components at the subtractor inputs.

radio simulation network where the low frequency

The FRPCM (pcm plus orderwire) signal Is passed

components of the signal are phase shifted and

through a low pass filter which eliminates the high

attenuated in the same manner as were the low

frequency components of the pcm signal but passes

frequency components of the FRPCM signal during

some low frequency components. This signal is applied

radio transmission.

The radio simulation network

to one input of the subtractor.

The pcm signal

consists of two sections: The first section provides for

(1RSPCM-2) was separated from the FRPCM signal and

simulation of the low frequency phase shift and a portion

reshaped in lA12AS, so it is not the same as the pcm

of the attenuation characteristics of the radio; the

component of the FRPCM signal. To equalize for this,

second section provides the additional phase shift and

the

amplitude,

phase

shift

and

attenuation

attenuation required to properly simulate the radio

characteristics of the pcm (1RSPCM-2) signal are

characteristics. The output of the radio simulation

modified so that they approximate the similar

network is applied to the second input of the

characteristics of the pcm component of the FRPCM

subcontractor (inverting input).

signal. The 1RSPCM2 signal is also passed through a

(4) The only difference between the two input

low pass filter.

The characteristics of the pcm

signals applied to the subtractor is the orderwire signal

components of the input signals are then approximately

which has been added to the FRPCM signal prior to

equal. The output signal of the, subtractor is applied to

radio transmission. The output of the subtractor stage

the audio amplifier and to a feedback circuit. The

therefore, is the orderwire signal plus a minimum

feedback circuit applies the output signal to the product

residual pcm signal. The orderwire signal is amplified

detector circuit If there is a residual pcm component in

by the af amplifier stage (Q6, Q7, Q8). The audio

the output signal, it is combined with the lRSIPCM-2

amplifier has an adjustment for gain and a low-pass

signal in the product detector. The output of the product

network to attenuate the residual pcm. The output of

detector, through the differential amplifier, controls the

the amplifier (RRW) is applied to orderwire assembly

amplitude of the pcm (lRSPCM-2) signal input to the

IA13 for further processing. A level detector circuit at

residual pcm component at the output of the subtractor

the output generates a dc voltage when the orderwire

to a minimum.

signal is active. The dc voltage is available at a test

(1) The FRPCM signal from Receiver, Radio

point for monitoring and testing purposes.

R-1467/GRC-144 is passed through a 50 kHz low-pass

g. AF Amplifier 1A12A6 (fig. 5-8 and 534). The

filter to remove high frequency components before

radio-to-cable circuits of af amplifier 1A12A6 amplify the

processing. At the output side of the filter, the signal

"cable ow in" signal (CCOWIN) for orderwire assembly

consists of orderwire plus residual pcm and noise

1A18.

The radio-to-cable circuits of 1A12A6 are

components below 50 kHz. The filtered signal is applied

comprised of an input level control, an input amplifier, a

to the noninverting input of the subtractor stage

lowpass filter with cutoff frequency of 2000 Hz and a

(differential amplifier Al).

power amplifier. The amplified output of 1A12A6, cable

(2) The 1RSPCM-1l signal is sliced by age

transmit ow (CCTOW), is applied to the primary side of

slicer Q4. The amplitude of the agc slicer output signal

transformer 1A12A12A2T2. A level detector circuit at

is controlled so that it is the same amplitude as FRPCM

the output generates a dc voltage when the orderwire

signal (approximately 1 volt peak-to-peak). Agc slicer

signal is active. The dc voltage is available at a test

amplitude is controlled by a dc signal from differential

point for monitoring and testing purposes.

amplifier Q2 and Q3. The dc signal is developed from

h. Alarm-Monitor, Synchronous Mode lA12A5 (fig.

the 1RSPCM-1 signal through a low-pass filter, buffer

5-8 and 5-33). The radio-to-cable circuits of alarm

amplifier Q1 and the product detector and from the

monitor 1AlaA5 control the RADIO TO CABLE MODEM

residual pcm from subtractor Al. The product of these

indicator on meter panel assembly 1A16A4 and the

signals produces a dc output from the rectifier and

shelter mounted traffic out indicator. Two kinds of

integration network which is applied to differential

Signal are monitored by the radio-to-cable circuits:

amplifier Q2 and Q3, which, in turn, controls agc slicer

functional alarm sig-

gain. The signal is then passed through a 50 kHz low-

pass filter, to remove the very high frequency

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