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BMX SERIES III CONSOLE
amplifier U4A. Dim relay K2, when energized, inserts a fixed 12 dB attenuator into the signal path. The
gain of U4A is 6 dB to recover the 6 dB loss of the Talkback insert circuitry. The output of U4A is
connected to the module FIXED OUTPUT LEFT terminal.
The "variable level" signal path includes the front panel MONITOR level control, Talk to Studio relay
K5, and buffer amplifier U5A. The gain of U5A is also 6 dB to recover the loss of the Talkback insert
circuitry. The output of U5A is connected to the module VARIABLE OUTPUT LEFT terminal.
The TALK TO STUDIO BUS-1 signal is summed and inverted by dual amplifier U1, and routed to Talk
to talent relay K3 and Talk to Studio relays K4 and K5. An additional output from U1 is connected to
the TALK TO STUDIO-1 OUT terminal. The resistor network around each of the Talkback relays
causes the monitor signal to be dimmed by 10 dB whenever the relay is energized to insert the Talkback
signal, and allows the Talkback signal to be inserted at unity gain over the attenuated monitor signal.
LOGIC
The Studio-1 monitor system may be muted by a low applied to the MUTE STUDIO-1 logic bus, or
by a low applied to the REMOTE MUTE input line. In either case, a low input will cause a high output
from gate U200D. This high is routed through Q201 to monitor mute relay K1, REMOTE MUTE
COMMAND transistor Q200, through inverter U203E to warning lamp driver circuit Q202 and Q203,
and to front panel TALK OVER MUTE switch S200.
The Studio-1 monitor system may be dimmed by a low applied to the DIM STUDIO-1 logic bus, or
by a low applied to the REMOTE DIM input line. In either case, a low input will cause a high output
from gate U200A. This high is routed through Q205 to drive dim relay K2, and to REMOTE DIM
DRIVE COMMAND transistor Q204. The logic bus dim command is also connected to internal option
switch S202 ("dim disables Talk"). This switch provides the ability to establish a one-way priority of
communication from the Studio by switching the DIM STUDIO command to inhibit the receipt of
TALK TO STUDIO commands. This is accomplished by closing switch S202, which then routes the
dim command through inverter U202C to Talk to Studio gate U201.
The TALK STUDIO-1 bus is driven low whenever a Microphone Input Module assigned to Studio-1
initiates communication to another location. This low is routed to Talk to Studio gate U201, and to
inverter U203D. Gate U201B provides the control logic for the TALK OVER MUTE feature. The
output of U201B is routed through inverter U202E to Talk to Studio relays K4 and K5. The output of
inverter U203D drives Talk to talent headphone relay K3 and REMOTE TALK COMMAND transistor
Q206.
4.7 MONAURAL LINE OUTPUT AMPLIFIER
4.7.1 Function
The Monaural Line Output Amplifier may select or mix any combination of the PROGRAM,
AUDITION and UTILITY stereo signals to produce balanced MAIN and AUXILIARY monaural
outputs.
PACIFIC RESEARCH & ENGINEERING
REVISION C
76
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