Wavetek 188 Manual page 20

When the СОМТ switch is released, trigger logic is іп-
hibited from passing any trigger signals and the trig-
ger flip-flop output is held high. This prevents the trig-
ger diodes from conducting and the generator loop
operates continuously.
When the CONT switch is pressed, the generator loop
is held at the ОМ baseline. Pressing the TRIG/GATE
switch puts the instrument in triggered mode and any
external or manual trigger signals at the trigger logic
input will be transformed into a narrow pulse cor-
responding to the low-to-high transition of the trigger
input. This pulse sets the trigger flip-flop high and
allows the generator loop to run. When the triangle
negative peak is reached, the comparator low-to-high
transition clocks the trigger flip-flop Гом and, when the
ОМ baseline level is reached, the generator loop again
stops. The result is a single cycle generated after
the triggering signal corresponding to 0 to 360° of
phase. Successive triggered waveforms always start
at the same 0° point.
Releasing the TRIG/GATE switch puts the instrument
in the gated mode. This is identical to the triggered
mode, except the trigger flip-flop is held high for the
full duration of the triggering signal. The generator
produces continuous waveforms during the time the
external signal is high or the manual trigger switch is
4-2
held in. The last ігіддегеа cycle started is always com-
pleted and successive gated bursts always start atthe
0° point.
When sweep mode is selected by a combination of
the main generator in continuous mode and the ramp
generator switches set to SWP, the ramp generator is
enabled and a ramp voltage becomes part of the con-
trol voltage in the VCG circuit to control the main
generator frequency. Ramp period, variable from
30 ms to 1 minute, is set by the TIME Control. Ramp
generator output is buffered to drive the sweep output
and VCG circuit. The ramp magnitude suppling the
VCG input is controlled by the STOP potentiometer.
Selecting the stop switch position biases the buffer
amplifier to a level equal to the positive peak of the
ramp (+ V). In this static mode the upper sweep limit
can be set by the STOP Control.
When the CONT position of the SWEEP switch is
selected the ramp generator is disabled and the buf-
fered ramp is disconnected from the VCG input.
The GCV (Generator Control Voltage) from the УСС
circuit is a resultant voltage from the three VCG in-
puts: dial, VCG ІМ and sweep ramp. This voltage is
buffered and made available at the GCV BNC.