Abstract: A system for providing a distinctive indication that a system, such as a security system, is in a test mode in which the distinctive indication includes audible and/or visual indications that a test sequence has been initiated, followed by testing of the system during the test sequence, with test results being indicated by altering the format of the audible or visible signal. In one embodiment involving a security system, a periodic signal is changed to a steady state signal when a sensor has been violated, thereby to provide a reminder that the system is in the test mode followed by instantaneous communication to the user of not only the operability of the sensor but also both the transmission of the sensor's output to a central control unit and the operability of this control unit itself.