Multiple switches control a light circuit a

In a, Sl and S2 are single-pole double-throw switches. When the switch is in the position in the picture, the light is on. In Figure b, Sl and S2 are single-pole double-throw
switches, and s3 is a double-pole double-throw switch. In this circuit, when any one of the three switches is flipped, the on and off state of the light will change. According to
needs, several double-throw switches can be added between S1 and S2 to connect multiple switches to control a lamp circuit .
Visually, you can see that the three colored lights EL1, EL2, and EL3 light up in sequence, which is very beautiful like running water.
    The diodes Dl~D4, D5, D7 and D9 in the figure are 1N4001, while D6, D8 and Dl0 are 2CP type rectifiers. Thyristors
VTH1 ~ VTH3 are 3CT type thyristors , whose reverse withstand voltage should be higher than 400V and current 1A.