A sound source switching circuit composed of thyristors

Introduce a thyristor sound source switching circuit that does not use integrated circuits, does not occupy relay contacts, has simple wiring, and is easy to expand.

When the power is turned on, the control terminals of SCR1-- SCR4 are in the off state without triggering current, and J1-- J4 do not operate. If J1 needs to be pulled in, press S1 and the current flows through R2 to charge C1. Point A becomes low to ground and T1 is turned off.

As C1 is charged, the potential at point B increases with the rise of the potential at point A. At this point, due to the current flowing through the control electrode of SCR1 for charging C1, SCR1 conducts, J1 is energized and attracted, LED1 lights up, and after releasing S1, J1 remains in the attracted state due to the action of SCR1, while C1 discharges through R1.

If J4 suction is required, press S4. Due to T1 being turned off first and then turned on, SCR1 is turned off due to power loss, J1 is reset, and then SCR4 is turned on and J4 is attracted. The principle is as described earlier. Similarly, if other relays need to be engaged, simply press the corresponding button.

If expansion is needed, simply add a unit circuit consisting of light-emitting diodes, relays, thyristors, and buttons.