Square Wave
Modulation
Operating
Modes
The 681XXC provides square wave (pulse) modula-
tion of the output signal using modulating signals
from either its internal square wave generator or an
external signal generator.
The signal generator’s internal square wave genera-
tor outputs modulating signals of 400 Hz, 1 kHz,
7.8125 kHz, and 27.8 kHz. The modulating signals
are selectable from a menu.
The 681XXC accepts modulating signals from an ex-
ternal signal generator that are TTL-compatible
with the minimum pulse width of >5 ms.
Providing
Square Wave
Modulation
The following are the menu selections necessary to
provide square wave (pulse) modulation of the out-
put signal using a modulating signal from both the
internal and external sources.
Press MODULATION. At the resulting menu dis-
play,press SqWave. The Square Wave Status
Menu (below) is displayed.
This menu contains the square wave status window
that shows the current menu selections. This menu
lets you perform the following:
qTurnsquare wave modulation on/off.
qSelect Internal or External source for the
modulation signal.
qSelect the polarity of the signal (High or Low)
that turns the RF on.
qGo to an additional menu (to select the fre-
quency from the internal source or to select the
front or rear panel input connector).
681XXC OM 3-77LOCAL (FRONT SIGNAL
PANEL) OPERATION MODULATION