Interface circuit for automatic counting with electronic counter a

The interface circuit for automatic counting using an electronic calculator is shown in the figure.
Figure (a) uses the travel switch so to be controlled by the photocoupler B;
Figure (b) uses the reed switch KR and pulse signal control;
Figure (c) uses the photocoupler B and pulse signal control, and the light-emitting diode VL is used to monitor the count Pulse operation;
Figure (d) is controlled by photoelectric tube LD and relay KA.