This circuit is working as two LED flip-flop that add with a same transistor circuit, then output voltage of each collector is feed to SCR gate (as seen at figure 1).

Figure 1. Running Lamp Circuit.

Figure 2. Thyristor FIR 3D Pin out, top view.

The reason of using SCR, because SCR is easy to control in ON-OFF mode at one way electric current. This circuit may be connected to more lamp with series L1-L2-L3-L1-L2-L3 and so on. How many lamp can be connected is depended on the lamp power (because of FIR 3D current limiting), each SCR is loaded with 50 watts for the safe condition, so if each lamp power is 2,5 watt (small lamp), then will be conneted to 60 pieces of lamp.

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