Electro-Metrics EM-2115, Instruction Manual

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EM-2115 APPENDIX C FUNCTION AND DESCRIPTION
(EM2115C-11)
2) End of sweep--pen lift.
b. Continuous Mode:
1) Sweep start--trace activated.
2) End of sweep--blanking activated.
3) End of blanking--sweep start initiated.
The Blanking circuit blanks out the external oscilloscope CRT during retrace of the spec-
trum display from right to left.
When the AFC function is turned on, the AFC voltage from the Discriminator circuit, via
the Audio Amplifier Board (A9), is applied to the Fine Tune circuit. Multiplexers, controlled by
the Microprocessor Board (A1A3), apply the AFC voltage to the Fine Tune circuit.
C-12 A9 Audio Amplifier Board
(Refer to Figure H.20)
The Audio Amplifier Board provides the AM/FM audio output for the receiver.
The AM Video (logged video signal) from the Detector Board (A8) is applied through an
amplifier/buffer circuit to a multiplexer. The multiplexer, controlled by logic commands from the
Microprocessor Board (A1A3), switches between the AM signal and FM Video signal. The se-
lected signal is applied to the audio amplifier circuit whose gain is controlled by the front panel
Audio Volume Control. The output of the audio amplifier is applied to the front panel Audio
Output Jack (A1J2).
In addition, whenever the AFC function is activated, the multiplexer switches the FM
Video for use by the Sweep Board (A11).
The circuitry for obtaining the peak level of a quasi-peak detected signal, is also located
on the Audio Amplifier Board (A9). A multiplexer is used to switch the dump on for this circuit
that is part of the Detector Board (A8) circuitry.
C-13 A12 Prescaler Module
(Refer to Figure H.21)
The Prescaler Module provides the correct outputs to the Microprocessor Board (A1A3)
for the proper scaling of the front panel Frequency Display.