Sierra Video Manzanita 321V - Manual (Page 8)

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Sierra Video Systems • P.O. Box 2462 • Grass Valley, CA 95945 • (530) 478-1000 • Fax (530) 478-1105
INSTRUCTION MANUAL
Model 321S Circuit Description
The electronics for the Model 321S are all on a
single plug-in module, the 503105. Refer to the
schematic diagram while reading the following
circuit description.
Each input signal is attenuated 10 dB by the
divider R1/R2 and buffered by an op amp
follower, U1. Each of the 32 stereo crosspoints on
the 503105 is made using a separate CD4066 IC,
U2. The audio switching on the 503105 is done in
the balanced mode at relatively high level (up to
30V P-P). This maximizes all possible audio
performance characteristics.
The 32 switching IC’s are tied together and feed
the output circuit which is based on U2. U2
provides common mode rejection and 10 dB of
gain to offset the input attenuator.
Control for the 503105 is in the form of a five bit
binary pattern at J3 pins 20 through 24. U11 and
U12 latch the incoming control selection. U13 and
U14 convert the 0 to +5V output of the latch to +/
- 8V. U8 and U9 decode the 5 lines to 1 of 32 to
select the desired crosspoint.
24VAC center tapped is produced by an external
power transformer. The low voltage AC enters the
module on J3 pins 27 and 28. It is rectified by D1
through D4. C1 and C2 are the positive and
negative primary filters respectively. U4 produces
+12V for the audio op-amps. U5 produces -12V
for the audio op-amps. U6 produces +8V for the
audio crosspoints. U7 produces -8V for the audio
crosspoints. U8 produces +5V for the latch circuit.
Remote control panel
The 503104 is a 32 switch circuit board which
uses LED lamps and includes switch encoding
and lamp driver circuits. The 503104 is primarily
used with the Model 321V, 324V and 321S, 32
input video and stereo audio switchers.
Refer to the schematic diagram while reading the
following circuit description. The 32 switches are
connected together in an 8 by 4 matrix configura-
tion. U1, U2, and U3 convert this to a 5 line
binary pattern. U4 and U5 convert this back to an
8 by 4 to drive the LED lamp array which is also
configured in an 8 by 4 fashion.
The 503104 is powered via the control cable. U6
provides regulated +5V DC.
Serial Control Protocol
The protocol is designed to use the 7-bit ASCII
character set, usually sent over a RS-232C serial
link at 9600 bps. The high-order data bit is
ignored on all received characters, and is 0 on all
transmitted characters.
The protocol is designed for use over a reliable
channel. Noisy channels, such as modem connec-
tions over the telephone network, should use an
error-checking and/or error-correcting protocol,
including such things as packet check sums or
CRC’s. Newer modems include such communica-
tion schemes as part of their normal operation,
and are recommended for these applications.
The protocol is designed to be compact, with few
characters required to cause switch changes to
occur. It is also designed to be human-readable
and thus easy to understand and use. Finally, it is
a modified subset of the existing SVS host protocol,
allowing a degree of compatibility with those
existing systems.
Several different switch request commands are
defined, so that the one that is most compact for
any given switcher and application can be chosen.
All input, output, and level numbers begin at
number 1, not 0.