Studio Technologies ISS - Manual (Page 28)

ISS User Guide Issue 3, June 1990
Studio Technologies, Inc. Page 29
ISS
create the right channel we subtract the
same amount. The amount we add and
subtract is directly related to how much
stereo effect we desire. Trim pot R43, Ste-
reo Depth, controls how much of N1’s
output is combined with the incoming
mono. Our resulting stereo signal for the
left channel is the sum of the input signal
(mono) and our stereo information; the right
channel is the difference between the input
signal and our stereo information. When
listening in MTS stereo, you hear a good
stereo “feel.” When listening in MTS mono,
the left and right signals are summed
(added together), giving you just the origi-
nal signal. Our stereo information simply
cancels out! Remember, what we added
to the left channel, we subtracted from the
right channel. Add left and right together
and our stereo information drops out. This
process holds true when we have two
simulator cards. The Type I Card adds and
subtracts full bandwidth stereo information.
The Type II Card adds and subtracts band-
passed stereo information. Add left and
right together and the stereo information
from both cards cancels out. Perfect mono
compatibility!
Mode Select Card
The Mode Select Card features a simple set
of logic circuitry that efficiently controls ISS
system operation. The Mode Select Card
directs and creates logic signals that are
sent to the Crossfade Card, which in turn
creates the signals you hear on the air and
observe with your remote controls.
Dual 4 input/1 output analog switch U8
serves to route logic signals to the simulate
from left and the simulate from right inputs
on the Crossfade Card.
The Mode select switch chooses one of
three operating modes. In the manual
mode, the Crossfade speed is held in the
SLOW position, and the X1/Y1 signals on
U8 are routed to the Crossfade Card. The
Manual front panel switch is then used to
control the Crossfade Card. This mode is
primarily intended for testing or special
applications.
In the AUTO mode, the FAST/SLOW speed
line is no longer held logic low, and the
X0/Y0 signals on U8 are routed to the
Crossfade Card. Signals originating from
the Recognition Card (if present in the
system) are processed and then sent to
X0/Y0. Three signals come from the Recog-
nition Card: R=L, L Only and R Only.
Logic Signal R=L
L Only R Only
Logic High X0 X0 Y0
Logic Low Y0 Y0 X0
FAST/SLOW Low for High for High for
Logic Slow Fast Fast
In the AUTO + REMOTE mode, the signal
going to the Crossfade Card depends on
the state of the B input to U8. When B is
logic low, remote control has not been
enabled and operation is the same as in the
AUTO mode. When B is logic high, remote
control has been enabled. The signals
present on X2/Y2 are sent to the Crossfade
Card. When simulate from left is requested
via remote control, X2 is high and Y2 is low.
When simulate from right is requested via
remote control, X2 is low and Y2 is high.
When no simulation is requested, X2 and
Y2 are low.
Four identical circuits buffer the remote
control inputs. Optocoupler integrated
circuits provide complete isolation between