This post explains for the Contactor.
The Part Number is 3TK2804.
The function of this semiconductor is Contactor Safety Combination.
Preview images :
THIS IS CONTACTOR COMBINATION FOR SAFETY CIRCUITS ENABLING AND SIGNALLING CIRCUIT. ( 4NO, 1NO+1NC DC OPERATION DC 24V )
Functions and connections :
The internal control circuit of the contactor safety combination is designed according to DIN EN 60204, Part 1 (VDE 0113, Part 1), para. 188.8.131.52, so that in the case of a fault in one of the contactor relays the function of the safety circuit is maintained. The supply voltage must meet the requirements of the DIN EN 60204 (VDE 0113, Part 1) (the terminals “L-/N; A2“ must be connected to that side of the control current circuit which is linked to the protective
The contactor safety combinations can be used in EMERGENCY-OFF circuits
and for monitoring protective devices (e.g. protective screens).
Other data sheets are available within the file: 3TK2804-0BB4