Single line control indicator light circuit a

In order to reduce the number of remote control connections, a single-wire control circuit can be used. The circuit is shown in Figure 13-46. Figure 13-46
(a) uses an ordinary light bulb as the indicator light, Figure 13-46 (b) uses a light-emitting diode as the indicator light . They are
designed to take advantage of the unidirectional conductivity of diodes.