Communications: electrical – Systems – Call station
Patent
1974-09-30
1977-01-11
Caldwell, John W.
Communications: electrical
Systems
Call station
62125, 331 65, 340248B, 340384E, G08B 2100
Patent
active
040030440
ABSTRACT:
Whenever power fails, an audio signal is produced by an oscillator, which includes a pair of transistors of opposite conductivity having the collector of each connected to the base of the other and is maintained in an off condition as long as the power is on. When the oscillator is turned on, a rapidly changing surge of current is supplied from a battery, which has a capacitor in parallel therewith, to an audio producing device in the discharge path of the oscillator. This surge of current is produced through utilizing a Zener diode between the battery and one of the two transistors of the oscillator. The parallel combination of a resistor and a capacitor is disposed between the Zener diode and the transistors of the oscillator. A resistor also is disposed between the emitter of the transistor initially turned on and a capacitor, which is charged to a potential to turn on the transistor. This resistor is of substantially lower impedance than a resistor between the capacitor and the battery. This arrangement increases the power at least two orders of magnitude.
REFERENCES:
patent: 3189788 (1965-06-01), Cady
patent: 3202937 (1965-08-01), Anderson
patent: 3748656 (1973-07-01), Gray et al.
patent: 3786342 (1974-01-01), Molyneux
patent: 3811122 (1974-05-01), Raber et al.
patent: 3863128 (1975-01-01), Wilwerding
Electronic Design; p. 122; Dec. 6, 1967 "Voltage to Frequency Converter Built with One UJT Oscillator."
Radio-Electronics; pp. 50-52; Oct. 1970; "How to Putter with the PUT."
Caldwell John W.
Leach, Jr. Frank C.
Myer Daniel
Wolsk Associates, Ltd.
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