One of the automatic periodic switching circuits

One of the automatic periodic switching circuits

The so-called automatic periodic switching circuit is a switching circuit that automatically and repeatedly completes the on, off, on and off actions after the power is turned on
. It is often used in situations where automatic intermittent control of the operation of motors and other equipment is required.
    The circuit is shown in the figure. The circuit consists of a single-junction transistor relaxation oscillator (VTl) and a bistable flip-flop
(VT2, VTa). The single-junction transistor relaxation oscillator emits pulses according to the time rules of ti = R1Cl and ￡2 = RzCt
to control the pull-in and release of relay KA. In this way, KA will act periodically according to these two time rules.