Abstract: An alarm communication device and a method for mutual recognition between a first alarm unit and a second unit connected therebetween by a public switching unit is provided. The first alarm unit is connected to the public switching unit via at least one first communication line and the second unit is connected to the public switching unit via at least one second communication line. The method includes the steps of detecting a ring signal at the first alarm unit, detecting a caller identification (ID) signal provided by the public switching unit, determining a caller ID number from the caller ID signal, matching the caller ID number with at least one predetermined number and when the caller ID number is matched to one of the at least one predetermined number associated with the second unit, executing a predetermined procedure associated with the matched at least one predetermined number.