• If you select the External source, the carrier waveform is modulated
with an external waveform. The modulation depth is controlled by the
±5V signal level present on the rear-panel Modulation In connector.
For example, if you have set the modulation depth to 100%, then
when the modulating signal is at +5 volts, the output will be at the
maximum amplitude. When the modulating signal is at -5 volts, then
the output will be at the minimum amplitude.