so does television, both transmitter and receiver. The circuits used
to produce the timing pulses are similar to those used in radar or
oscilloscopes. The timer is sometimes referred to as the
synchronizer or keyer. In general, there are two methods of
supplying the timing requirements.
(1) Timing by separate unit. The pulse repetition frequency
can be determined by an oscillator of any stable type, such as a
sinewave oscillator, a multivibrator, or a blocking oscillator. The
output is then applied to pulseshaping circuits to produce the
required timing pulses. Figure 9 shows typical combinations of
circuits which may be used as timers in television, radar,
multiplexers, and oscilloscopes.
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