ADT transmitter with digital processing of the measured values and temperature compensation for the continuous monitoring of the ambient air and detection of combustible gases and vapours. The calibration routine with selective access release enables the comfortable calibration of the transmitter. In addition to the standard analog output (0) 4-20 mA or (0) 2- 10 V DC the ADT-23 is equipped with a RS-485 interface for different protocols. Two relays with adjustable switch threshold are available as an option.