User`s manual

Both the “FSK” BNC connector and the TTLTrg<n> trigger lines use TTL
compatible signal levels. A “high” level on the BNC or trigger line selects
frequency1, a “low” level selects frequency2.
Frequency-Shift
Delay
Once the control signal to shift the frequency is received, there is a delay of
20 reference oscillator clock cycles before the frequency is active. This
delay occurs with all reference oscillator sources.
Driving the
TTLTrg<
n> Trigger
Lines
When driving the TTLTrg<n> trigger lines with the Agilent E1406A
Command Module, note that the module uses negative-true logic. Thus,
writing a logic ‘1’ to a trigger line sets the line to an electrically low level.
This would select FSK frequency2. Writing a logic ‘0’ to a trigger line sets
the line to an electrically high level which selects frequency1. Refer to your
Command Module manual for more information on setting up and enabling
the TTLTrg trigger lines.
162 Sweeping and Frequency-Shift Keying Chapter 4