Prevent misoperation of control circuits in both places

Using the circuit shown in Figure 4133 can prevent misoperation between the two places. When it is necessary to start,
the operator at location A presses the start button SB2. At this time, the buzzer
HA2 installed at location B can only sound. When the operator hears the bell, he presses the start button. After pressing the button SB3, the buzzer HA1 installed at ground A will buzz for a long time, and then the contactor KM will be energized to attract and self-energize. Its main contact will be closed, and the motor M will start. At the same time, the KM will switch off. The contacts are disconnected, causing HA1 and HA2 to lose power. When parking is required, the operator at location A can press SB1, and the operator at location B can press SB4.