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10
PROGRAM LINE OUTPUT
The only guarantee of protection against transmitter overmodulation is
a short and direct connection between the output of the Model 235
Processor and the transmitter input. Any frequency or phase error
between the Processor and transmitter will partially (or completely!)
negate the tight final peak control which the 235 provides.
This means that the 235 must be located
at the transmitter site
to be
completely effective. Even a digital link (STL, ISDN, FRAC-T1 or
FDIC) will compromise the peak control function. Moreover, the
interconnect cable should be kept short and direct. Less than 10 feet of
a shielded, twisted pair is preferred.
Output
Connection and
Signal Phase
The
LINE OUTPUT
of the 235 Processor terminates at the removable
barrier strip on the rear panel. This output is electronically-balanced
(transformerless) and
must be connected to the input of the transmitter
with proper regard to signal phase.
Output terminals are marked
+
and
–
. These should be connected to
similarly-marked transmitter input terminals. The output program
signal from the 235 will exhibit waveform asymmetry in the direction
indicated; that is, the + terminal will be (additionally) positive-going
with (increased) positive peaks. Make sure that the + terminal is
connected to the transmitter input terminal which yields an increase in
carrier level for a positive signal excursion.
REAR-PANEL “MODE” SWITCH
The 3-position toggle switch on the rear panel of the 235 selects
OPERATE
, for local (front-panel) operation,
REMOTE CONTROL,
for
processor control by computer or modem through the RS-232 port, and
PROOF
, which effectively bypasses the unit.
The switch must be left in the
OPERATE
position if front-panel buttons
are to be used for setting processing parameters. Once set, the switch
may be switched to
REMOTE CONTROL
position to lock-out the front
panel buttons and protect Processor setup. When it is in the
OPERATE
position, the Processor
will not respond
to remote, RS-232 commands.
The switch must be set to
REMOTE CONTROL
to activate the RS-232
port for remote computer or modem control. See appropriate
instructions for remote Processor operation beginning on Page 15.
PROOF
completely bypasses the functions of AGC, compression, pre-
emphasis, equalization, limiting, clipping and the low-pass output filter.
It effectively turns the Processor into a line amplifier, though the
subsonic, 50Hz high-pass function is still active.
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