is coupled across the emitter and collector of transistor 106 thus acting as a protection device for transient relief the emitter of transistor 106 is further connected to the electromagnet voltage supply 23 preferably a battery and the collector of transistor 106 is further connected to the electromagnet 20 the pin 82 of the buffer chip 66 is also coupled with a pin 112 of a darlington driver chip 110 which operates as a current sink dependent upon the logic level and is connected from pin 114 to the electromagnet 20 in conjunction with the collector of transistor 106 the pin 90 of buffer chip 66 is connected to a pin 116 of the driver chip 110 which is in turn coupled from pin 118 to the electromagnet 20 in conjunction with the collector of the transistor 100 this configuration allows the current flow to the electromagnet 20 to be alternated or shut off completely by the microprocessor 24 thus providing the switch 22 the driver chip 110 is connected to the signal ground wire 95 through a pin 118 and is connected to the electromagnet voltage supply 23 through a pin 120 which is further coupled through a series capacitor 122 to the signal ground wire the signal ground wire 95 is connected to pin 124a of the connector port 74a the connector port 74a has pins 126a 128a and 130a connected to ground and has pin 132a connected through a diode 134 to the electromagnet power supply 23 the buffer chip 66 has pin 136 connected to the constant voltage source.