MCB-CLICK-... modules allows contactless acquire sugnals from databus of car. Essence of their operation is "reconstructing" of signal from vehicle databus, but without electrical/physical connections to this databus.

Modules exclusively acquire signals (read data) - isn't ("physically") possible to transmit "anything" to the databus of car. Outputs of the module are wires with "identical" signal like on databus of car. Signal obtained in this way can be connected to any, 3rd party device which require CAN-Bus signal on input side.

This way module protects against errors of connection 3rd party devices to the databus of car and also against "formal problems" from producer/warrantier of car in subject "possible interferences to signal system of the vehicle".