Control geography capable of issuing start and stop signals

For some large-scale mechanical equipment, the moving parts driven by the motor have a large range of movement, so a starting signal needs to be sent before starting, and
the motor will be started after a period of time to inform the staff and maintenance
personnel stay away from the equipment, as shown in Figure 4-28 The circuit shown enables
the function of automatically sending out a start signal.
    To start the pair, press the button SB2, the relay KA will be energized
and self-locking, its moving and closing contacts will be closed, and both the bell and light will send out starting
signals . At this time, the time relay KT will also be energized at the same time. After
Imin (the time can be Adjust the connection as needed), the KT moving closing contact delays
closing, the contactor KM coil is energized, the KM main contact closes, the moving closing
auxiliary contact self-locks, the motor M starts to run, and at the same time due to
the pull-in of KM, its moving The broken contacts disconnected KA and KT, and the bell
and light bulb lost power and stopped working.