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BMX SERIES III CONSOLE
low command may be routed by option switch S200-4 through inverter U201E and gate U202B to hold
the input of U201B high. This high locks out the Talk to Control Room logic, and establishes a priority
of communication in the Control Room's favor.
The CUE system is activated whenever a low is applied to the CUE logic bus. This results in a high
output from inverter U201D, which is routed to auto-CUE relays K5 and K6 and the CUE TO METER
SW output.
The SOLO system is activated whenever a low is applied to the SOLO logic bus. This results in a high
output from inverter U201C, which is routed to SOLO relay K2 and the SOLO TO METER SW output.
4.6 TWO-STUDIO MONITOR MODULE
4.6.1 Function
The Two-Studio Monitor Module is expressly designed for applications where separate voice/announce
booths or conference Studios are required. This module provides the monitor, headphone and Talkback
facilities for up to two Studios. Monitoring of PROGRAM, AUDITION, UTILITY, or any of nine
external sources is provided by means of an interlocking monitor selector.
The module consists of a common monitor source selector and two identical sets of "guest" and "talent"
headphone outputs, fixed and variable level monitor outputs, and Talkback to Studio circuits. Each
section of each Studio's monitor circuitry has a relationship with the others which can best be
appreciated by reviewing the module block diagram located in Chapter 7 of this document.
4.6.2 Circuitry
AUDIO
NOTE: The stereo audio paths for the monitor and headphone sections consist of two identical sets
of circuitry. For clarity and simplicity, only the left channel of the Studio-1 section is described below.
The input to the Studio monitors is selected by the front panel 12-station push button switch assembly,
and routed to the balanced, symmetrical input, instrumentation amplifier. This amplifier is configured
with three operational amplifiers contained on plug-in function amplifier A1, operating with cross-
coupled input stage feedback. The voltage gain from module input to the output of the instrumentation
amplifier is -8 dB. The output of this stage is connected to the module MONITOR SELECT OUT
terminals, to Talk to talent headphone relay K3, and to the input of mute Studio relay K1.
The output of Talk to talent headphone relay K3 is buffered by amplifier U3A, which operates with 6
dB of gain to recover the 6 dB loss of the Talkback insert circuit. The output of U3A is connected to
the module TALENT HEADPHONE OUT terminal.
The output of the mute Studio relay is routed through dim relay K2 and feeds both the fixed and variable
level monitor circuits. The "fixed level" signal is routed through Talk to Studio relay K4 and buffer
PACIFIC RESEARCH & ENGINEERING
REVISION C
75
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