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REVISION C
BMX SERIES III CONSOLE
97
PACIFIC RESEARCH & ENGINEERING
S3-2 causes the Studio-2 dim function to block incoming Talkback signals to Studio-2. This switch is
identical to the Two-Studio Monitor Module option switch (see Section 2.9.4, page 46 for switch
location).
CIRCUITRY
NOTE: The Studio-1 and Studio-2 audio and logic paths consist of identical sets of circuitry. For clarity
and simplicity, only the Studio-1 audio and logic paths are described below.
Audio
The TALK TO STUDIO-1 bus signal is summed by U2A, amplified by U2B, and routed to the TALK
STUDIO-1 output terminal.
The TALK FROM STUDIO-1 signal is fed to balanced differential input amplifier U1A. This signal
feeds Talk to Control Room relay K1. When closed, Talkback audio is directed to summing resistor
R11, and to the TALK TO CONTROL ROOM audio bus.
Logic
The TALK TO CONTROL ROOM input command forces the output of gate U10D high. Transistor
Q13 conducts, causing Studio-1 Talk relay K1 to close. The output of U10D also feeds the input of gate
U10B. The output of this NOR gate is inverted to drive TALK TO CONTROL ROOM bus switch Q14.
These logic functions allow received Studio-1 Talk to connect to the console TALK TO CONTROL
ROOM bus.
The five external commands are activated by three internal control buses. The MUTE STUDIO 1 bus
is inverted by gates U6F. This gate output drives MUTE OUTPUT switch Q1 and the WARNING
COMMAND driver, consisting of inverter U7E, Q2 and Q3. The MUTE STUDIO 1 command
connects to gate U8B through the E1 to E2 jumper or the TALK OVER MUTE switch (when it is in
the disengaged position). The output of U8B is inverted by U9E to turn on TALKBACK WITH MUTE
switch Q5. Note that OR gate U8B is used as an inverted NAND gate.
The DIM STUDIO 1 bus command connects to gate U6A, is inverted, and drives DIM OUTPUT switch
Q4. This bus signal also feeds DIM DISABLES TALK switch S3, which disables gates U8C and U8B
from operating Talkback output switches Q5 and Q6.
The TALK STUDIO 1 bus will force gate U8C low if switch S3-1 is open. This gate output will be
inverted by U7D to drive TALKBACK OUTPUT switch Q6 low. The output of U8C connects to U8B,
which will allow the TALKBACK WITH MUTE switch to go low if the E1 to E2 is installed or the
TALK OVER MUTE switch is disengaged.