Abstract: An audible output device, of a type usable in a fire alarm system, incorporates a multi-frequency waveform generator. The generator produces a plurality of frequencies with predetermined duty factors during various time intervals on a repetitive basis. The multi-frequency drive signal is in turn coupled to an audible output device such as a piezoelectric horn or the like. The multi- frequency audio output provides an indicator to persons adjacent to the device of the presence of an alarm condition.

Abstract: An audible output device, of a type feasible in a fire alarm system, incorporates a multi-frequency wave form generator. The generator produces a plurality of frequencies with predetermined duty factors during various time intervals on a repetitive basis. The multi-frequency drive signal is in turn coupled to an audible output device such as a piezoelectric horn or the like. The multi-frequency audio output provides an indicator to persons adjacent to the device of the presence of an alarm condition.

Abstract: Parameters defining operational characteristics of audible, visual or audible/visual alarm indicating output devices, can be transmitted to the respective devices from common output control circuitry to avoid having to set up the devices electromechanically in the field upon installation, or upon replacement for maintenance purposes. The downloaded parameters can be stored locally at the respective device and can include prerecorded verbal messages, horn or chime output volumes, tonal patterns and repetition rates. Candela settings for strobes can also be downloaded from the control circuitry.

Abstract: A variable candela strobe unit couples a substantially constant trigger voltage to a trigger electrode of a gas discharge tube irrespective of the voltage provided across the tube which is specified by a selected candela output value. The trigger voltage is great enough at low candela output settings to provide reliable triggering. It is not high enough even at the highest output settings to cause arcing of the associated step-up transformer.

Abstract: A variable output strobe unit includes a variable current limiting circuit to limit peak current draw after each flash. Parameters of strobe output and current limiting circuit are related and can be set manually or electronically.

Abstract: Newly installed electrical units emit, for a brief install interval, an “installed” output either audibly or visually, or both in response to an install mode input signal. After the install interval, the “installed” output ceases. As more units are installed, the earliest installed units remain silent in the presence of the install mode input signal.