Relay power saving circuit one b

When the relay pulls in, a larger starting current is needed so that the relay can pull in reliably. After pulling in, only a smaller
current can maintain its pull-in state to achieve the purpose of power saving.
    Relay power-saving circuits are also suitable for contactors, electromagnets, and solenoid valves in principle.
(1) One of the relay power-saving circuits.
    The circuit is as shown in the figure. The input signal of the circuit in Figure (a) is DC. Adjust the capacitor C to make the relay
KA reliably pull in, and adjust the current limiting resistor R so that the KA keeps the current at a minimum but can reliably pull in the relay. The input signal of the circuit in Figure (b) is a pulse signal.