US 5,687,228 A · Universal amplified telephone handset

Abstract

An amplified telephone handset includes a current sensing circuit that senses the polarity of DC voltage supplied from a telephone base, irrespective of whether the DC voltage is of standard or reverse polarity. This feature allows the amplified telephone handset to operate with telephone bases that supply voltages through a telephone cord of either standard or reverse polarity. The amplified telephone handset also includes a voltage detection circuit that detects "off-hook" or "on-hook" states by detecting the absence or presence of the voltage. If a DC voltage is detected, then the amplified telephone handset is coupled to the telephone base and the voltage detection circuit disconnects the battery from receiver and transmitter circuits in the amplified telephone handset, placing the amplified telephone handset in a "on-hook" state. Conversely, when the amplified telephone handset is removed from the telephone base and no charging voltage is present, the voltage detection circuit connects the battery to the receiver and transmitter circuits in the amplified telephone handset, placing the amplified telephone handset in the "off-hook" state. An LED indicator on the amplified telephone handset indicates the level of electrical charge of the battery by the intensity of the LED diode.

Claims8

Dependent claims

An amplified telephone handset coupled to a telephone base via a telephone connector, the handset comprising:

a receiver amplifier electrically coupled to the telephone base to receive telephone signals via the telephone connector, for amplifying the received signals;
a transducer coupled to the receiver amplifier to produce the amplified signals;
an electrical storage device electrically coupled to the receiver amplifier for providing electrical power thereto;
and
a current sensing circuit having electrodes coupled to the telephone connector and receiving therefrom a standard polarity voltage signal or a reverse polarity voltage signal, the current sensing circuit having a first subcircuit for receiving the standard polarity voltage signal and a second subcircuit for receiving the reverse polarity voltage signal, each subcircuit producing a respective voltage signal in a mutually exclusive manner to couple the electrical storage device to the receiver amplifier.

2 more elements

Dependencies are inferred from the claim text.

Universal amplified telephone handset

Life of this patent

Universal amplified telephone handset

Life of this patent

Abstract

Claims8