These are surplus parts from Dulles International Airport. They were spares and were never used, packaging has some stickers, dust and writing but the part is in Excellent Brand New Condition.

The Siemens Model CZM-4 is used with the MXL to provide four Class A or Class B conventional initiating device circuits. Each circuit unit can monitor up to thirty 2-wire photoelectric or ionization smoke detectors and an unlimited number of normally open contact devices. Projected beam and flame detectors, detector relay bases, and remote indicator lamps may also be used with the CZM-4.