Studio Technologies ISS - Manual (Page 16)

ISS User Guide Issue 3, June 1990
Studio Technologies, Inc. Page 17
ISS
go out, making the Remote Simulate
from Left and Remote Simulate from
Right inputs inactive.
11) If you have connected the Status Relay
Outputs, you can test them now. Any
time the I/O NORMAL LED is not lit, the
ISS I/O Bypass Enabled relay contact
will close (short). The device connected
to this contact should indicate this
condition.
Any time the CORRECTING LED on the
Polarity Correction Card is lit, the Polar-
ity Correction Taking Place relay con-
tact will close (short). The device
connected to this contact should indi-
cate this condition.
Any time the REMOTE DISABLE LED
on the Polarity Correction Card is lit,
the Polarity Correction Function Dis-
abled relay contact will close (short).
The device connected to this contact
should indicate this condition.
Any time the SIM LEFT LED on the
SYSTEM STATUS section is lit, the ISS
Simulating from Left relay contact will
close (short). The device connected
to this contact should indicate this
condition.
Any time the SIM RIGHT LED on the
SYSTEM STATUS section is lit, the ISS
Simulating from Right relay contact will
close (short). The device connected
to this contact should indicate this
condition.
Any time the REMOTE LED on the
SYSTEM MODE section is lit, the ISS
Remote Control Enabled relay contact
will close (short). The device connected
to this contact should indicate this
condition.
Normal Operation
You should now feel confident that the ISS
has been carefully installed and tested, and
is ready to go to work in the exciting TV
business. (You remember excitement...
that’s 3am Monday morning working on the
transmitter!) Seriously, if you have any
questions concerning the ISS, now is a
good time to give us at Studio Technolo-
gies a call. Otherwise, set the front panel
controls to your desired operating mode
and that’s it. If one or more remote control
signals have been connected, be sure to
set the appropriate switches to allow re-
mote operation. You’ll most likely want the
SYSTEM MODE switch in either the AUTO
or the AUTO + REMOTE position.
Technical Notes
Definition of Level
Studio Technologies has opted to use the
dBu designation as it seems to be quite
rational. Using dBm was fine when all audio
line outputs were terminated with 600 ohm
loads. In this way, it is easy to say that
0dBm is 1 milliwatt dissipated in the known
load (i.e., 0dBm across 600 ohms will
measure 0.7746V). In contemporary situa-
tions, an audio output line is rarely termi-
nated in 600 ohms; generally 5k ohms or
higher. The dBu designated is a better
reference because it refers to dB referenced
to 0.7746V, with no reference to load im-
pedance. This takes into account today’s
audio scene with load impedances varying
greatly. When the ISS specifications refer
to the maximum output level in dBu, this
would translate to dBm only when the
output is terminated with 600 ohms.