Abstract: A voltage enhancement device in the nature of a DC-to-DC converter is used in a centrally monitored alarm system of the type having at least one alarm detection device at a first location, an alarm monitoring panel at a second location, and telephone lines interconnecting the device in the panel. The telephone lines have an internal resistance which causes some of the voltage applied at the input of the lines at the first location to be dropped thereacross with resultant decrease in voltage at the second location. The alarm monitoring panel includes an indicator, such as a meter, which requires a minimum detectable voltage to provide a suitable indication or deflection of the meter to distinguish between an alarm, normal or trouble condition at the first location.

Abstract: An improved alarm system is disclosed which includes one or more remote stations. Each remote station is connected to the central or control station by only three conductors or leads. The control and remote stations each include a pair of back-to-back LED diodes, the diodes of each pair emitting a different color light when current flows therethrough. The control and remote stations each also includes a key switch which is operative to "enable" and "disable" the alarm circuitry at the control station. By controlling the direction as well as the wave shape of the currents passing through the LED diodes, five different visual signals may be provided at the control and remote stations to indicate the status of the alarm system. Actuation of any of the key switches reverses the current through the LED diodes so that the different colors are indicated when the alarm system is "enabled" or "disabled".