output za is also fed back through resistor r27 to input 2a to maintain output za 34 high 34 capacitor c10 between the base and collector of transistor t1 suppresses noise the conduction of transistor t1 turns transistor t2 34 on 34 to energize set coil s of the relay for this purpose current flows from the 28 volt source through conductor 22 set coil s and transistor t2 to ground this set coil closes power contacts 20a 20b and 20c in fig1 as well as cutthroat contact ct in fig8 and the relay magnetically latches these contacts closed zener diode zd4 across transistor t2 protects the latter from high voltage peaks since the relay is now latched closed darlington pair q2 may be turned off this occurs in response to the aforesaid closure of contact ct which removes the 34 low 34 and applies a 34 high 34 to select input s0 of the multiplexer as a result both select inputs s0 and s1 now have 34 highs 34 whereby data at inputs 3a and 3b are routed to the respective outputs za and zb since input 3a is at ground a 34 low 34 darlington pair q2 is turned 34 off 34 but the relay remains latched as aforesaid until the trip coil is energized since input 3b is connected to overload trip conductor olt coming from the detector module the system is now in readiness to trip in response to an overload signal the trip action of this two unit digital multiplexer is defined by the following boolean equation the first set of three and conditions unl u00b7 ct u00b7.