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: 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 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: 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: 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.

Abstract: A selectable candela strobe alarm unit includes an energy storage circuit to reliably discharge a gas filled output device. The circuit includes a primary energy storage capacitor and a secondary energy storage capacitor. The capacitors can be configured in series or in parallel to produce a selected candela output from the gas filled output device.

Abstract: An electronic circuit, capable of being fabricated as an integrated circuit, for inclusion within a programmable radio for providing the radio with sleep and nap type functional operations. The electronic circuit includes a radio circuit coupled to a control circuit having a timing circuit, a time set circuit, a manually operated switch and a circuit coupling. The circuit couples the timing circuit, the manually operated switch and the time set circuit to the radio circuit to supply the radio circuit with first and second signals when the coupling circuit is in a first state and to prevent or block the first and second signals from being supplied to the radio circuit when the coupling circuit is in a second state.

Abstract: A circuit for controlling the brightness of a vacuum fluorescent display having filament terminals and connected to anode or segment biasing means includes a transformer having a filament winding connected to the filament terminals. The transformer is driven by a 60-cycle power source. An electronic switch, including a transistor, is connected between a center tap of the filament and the anode biasing means (at a common ground) and circuit means open and close the switch at a 60-cycle rate. The ratio of time during which the switch is closed to the time during which the switch is open is variable to control the brightness of the display.

Abstract: A brightness control circuit for use with light emitting (LED) displays, or comparable electronic displays that are energized from a source of DC potential that supplies periodic pulses of constant peak current to the display elements, the display brightness being controlled as a function of the pulse duty cycle so as to achieve a uniform and continuous control of the display over a relatively wide range of brightness levels, extending particularly into the lower brightness region. Energizing current is coupled to the display by a transistor switching means actuated at a given frequency and with a duty cycle that is a function of the brightness control setting.

Abstract: An inexpensive DC power supply including a primary DC voltage source generating a voltage with an inherent ripple content that is coupled to energy receiving circuitry by an emitter follower switching circuit under the control of a secondary DC voltage source of relatively constant voltage amplitude, so as to apply to said energy receiving circuitry a voltage with the constant amplitude characteristics of the secondary voltage source and at relatively high current levels which are generated by the primary voltage source. By adjusting the magnitude of the secondary voltage applied to the emitter follower circuit, ripple may be substantially eliminated from the voltage applied to the energy receiving circuitry by virtue of this applied voltage being established below the ripple component of the primary DC voltage.