Cordless telephone having power failure detection circuit

Details Cordless telephone having power failure detection circuit Cordless telephone having power failure detection circuit

1995-11-21

1997-08-26

Cumming, William

Telephonic communications

Audio message storage, retrieval, or synthesis

H04Q 700

Patent

active

056617801

ABSTRACT:
A cordless telephone can include a base unit including a cordless telephone circuit, a power source circuit and a resistor connected between a pair of power output terminals of the power source circuit, and a handset unit including a cordless telephone circuit, a secondary battery, a circuit connected between a charging terminal which receives power supply output from the power source circuit and a terminal of the secondary battery and consisting of a diode and a resistor connected in parallel to each other and a power break detection circuit. The secondary battery is usually charged by power supply from the power source circuit via the charging terminal and diode when the handset unit is placed in a cradle of the base unit, and electric power is supplied from the secondary battery to the cordless telephone circuit in the handset unit to operate in intermittent reception mode. When a break in power occurs at the base unit, the voltage at the charging terminal is dropped to a voltage level obtained by dividing the charged voltage at the secondary battery with two resistances which is lower than a reference voltage. Accordingly, the power break detection circuit outputs a power break detection signal having a low logic level to enter the handset unit in sleep mode.

REFERENCES:
patent: 4075510 (1978-02-01), Pascente
patent: 4761722 (1988-08-01), Pruitt
patent: 4894856 (1990-01-01), Nakanishi et al.
Abstract of JP 2-23753, Masahiro Fukuda, "Cordless Telephone System", Jan. 25, 1990.
Abstract of JP 1-177748, Hiroshi Furumura, "Cordless Telephone Set", Jul. 14, 1989.
Abstract of JP 3-85847, Keiichiro Sumikawa, "Cordless Telephone Set", Apr. 11, 1991.
Abstract of JP 3-60556, Keiichiro Sumikawa, "Cordless Telephone Set", Mar. 15, 1991.
Abstract of JP 4-167849, Takashi Ui, "Cordless Telephone Set", Jun. 15, 1992.
Abstract of JP 3-160843, Isamu Matsuda, "Cordless Telephone System", Jul. 10, 1991.

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