The ergonomic base handle CAPBs® ST is equipped with three magnets at the rear side. The battery compartment and the unlock button for exchanging the CAPBs® sens are also located at the rear. The snap-in mechanism on top of the base handle is standardised for all CAPBs® sens. A multi-purpose key is located at the front; it is used for switching the unit on and off, for zero adjustment, for activating the Hold mode or for starting the data logger function. The multi-colour LED displays the status of the CAPBs® measuring unit by means of different colours and flashing frequencies. For example, BLUE means "Establishing Bluetooth® connection" or GREEN "Connected to an evaluation unit". The base handle also contains a device which indicates excess concentrations or limit values by means of audible signals with different frequencies.