REVISION C
BMX SERIES III CONSOLE
84
PACIFIC RESEARCH & ENGINEERING
control bus. The high output of U15C is also routed through delay circuit R125, C100 and U19A to
Talk to Studio-1 relay K2A, which routes the Talkback signal to the TALK TO STUDIO-1 audio bus.
The high output of U15C is also routed through U22A to U20B, and causes a high to appear at the output
of U20B. This saturates Q7, pulling down the DIM C/R BUS.
Operating the console STUDIO-2 button causes a chain of events schematically similar to operating
the STUDIO-1 button. When the STUDIO-2 button is pressed the output of U15D goes high, which
is routed to U21B which then goes high, driving Q4 to pull down the Talk to Studio-2 control bus. The
high output of U15D is also routed through delay circuit R127, C101 and U19B, to Talk to Studio relay
K2B, which connects the audio signal to the TALK TO STUDIO-2 mix bus. The high output of U15D
is also routed to U22A, U20B to DIM C/R BUS transistor Q7.
Pressing the EXT Talkback button on the console causes a high output from U15E, which is routed
through delay circuit R129, C102 and U19C, to Talk to External relay K3A. The high output from U15E
is also routed through U22A and U20B to DIM C/R BUS drive transistor Q7, and through U21C to
TALK TO EXT CMD transistor Q6.
The Producer’s Talkback functions are a duplicate of the console’s facilities, so that the Producer may
also Talk to the same locations.
Pressing the Producer’s STUDIO-1 button causes a high output from U15F, which is routed through
U21A which then goes high, driving Q3 to pull down the Talk to STUDIO-1 logic control bus. The
high output of U15F is also routed through delay circuit R131, C103 and U19D, to Talk to Studio-1
relay K3B, which routes the Talkback signal to the TALK TO STUDIO-1 audio bus. The high output
of U15F is also routed through U22B to U20B, which saturates Q7, pulling down the DIM C/R BUS.
Operating the Producer’s STUDIO-2 button causes a chain of events schematically similar to operating
the STUDIO-1 button. When the STUDIO-2 button is pressed, the output of U16A goes high, and is
routed to U21B which then goes high, driving Q4 to pull down the Talk to Studio-2 control bus. The
high output of U16A is routed through delay circuit R133, C104 and U19E, to Talk to Studio relay K6A
which connects the audio signal to the TALK TO STUDIO-2 mix bus. The high output of U16A is also
routed to U22B, U20B and Q7 to the DIM C/R BUS.
Operating the Producer’s EXT Talkback button causes a high output from U16B, which is routed
through delay circuit R135, C105 and U19F, to Talk to External relay K6B. The high output from U16B
is also routed through U22B and U20B to the DIM C/R BUS drive transistor Q7. The high output of
U16B is also routed to gate U21C to drive TALK EXT CMD logic bus transistor Q6.
The microphone preamplifier for the External location is very similar to that for the Producer’s
microphone. It makes use of both halves of dual amplifier U3, with the front panel EXTERNAL INPUT
adjusting the level. The External preamplifier has a switchable pad, located before the input transformer
in order that line-level input signals can be accommodated. The EXTERNAL remote controls operate
similarly to the Producer controls, with the addition of the ability to Talk to the Control Room.
