Abstract: An electronic thermostat circuit has improved power stealing for controlling an AC control device. The circuit comprises a source of AC control power coupled to an electronic switch means having an electronic switch means control input. The electronic switch means controls the AC control device. The diode bridge controls the electronic switch means by a DC control signal applied to the diode bridge means DC connection. The amplifier means has an amplifier input for controlling the state of the amplifier and an amplifier output for generating the DC control signal. An isolated gate FET means is electrically coupled to the amplifier input for controlling the state of the amplifier. The isolated gate FET means is powered by the current derived from the source of AC control power by power stealing. The digital signal controls the state of the AC control.

Abstract: Telephone line status indication is improved by making measurements of the differential voltage across the Tip-Ring terminals of a telephone set. The telephone set is connected to a telephone line which is shared with other parallel-connected sets. The measurement of differential line voltage is made time the set changes state (i.e., between on-hook and off-hook). The maximum magnitude of one of the last three measurements is stored to represent the state, and is arithmetically averaged with the maximum magnitude of one or the last three stored for the oil-hook state to create a reference voltage. The reference voltage is updated each time the telephone set changes state and is continually compared with the present differential line voltage to determine which one is larger A light-emitting-diode on the telephone set indicates that the telephone line is in use whenever the reference voltage exceeds the measured differential line voltage.

Abstract: An adaptive expander for telephones reduces the gain of a transmitting amplifier in proportion to the intensity of the background noise. Gain reduction occurs when the user is not speaking into the handset microphone. When the user is speaking, however, the gain of the transmitting amplifier is restored to its normal level. Noise is distinguished from speech via long-term averaging of the microphone output signal, and a circuit that precludes the magnitude of the long-term average voltage from ever exceeding the short-term average voltage. The present invention is used in full duplex arrangements where simultaneous transmission in both directions is possible rather than in half duplex arrangements, such as a speakerphone, where transmission occurs only in one direction at a time.

Abstract: A voice-switched telephone circuit with center idle state improves bi-dirional gain control in loudspeaking telephones and thereby enhances the natural quality of interactive conversation. The voice-switched telephone includes: a transmit channel having a microphone and a three-state amplifier; a receiver channel having a three-state amplifier and a loudspeaker; and a hybrid circuit interconnecting the transmit and receive channels to a two-wire telephone line. The present invention is characterized by independent signal level detecting circuits for the transmit and receive channels. When the magnitude of the signal energy in the transmit channel exceeds a predetermined threshold, the transmit channel amplification is increased and the receive channel amplification is decreased by fixed equal amounts.

Abstract: The present apparatus for controlling the application of telephone line power in a telephone set has obviated the requirement for a local source of power at the premises of a telephone customer. A data processor-based telephone set incorporating the present invention comprises a power supply having first and second voltage storage devices (C401, C402) which accumulate charge from the telephone line. First and second regulator circuits (410, 420) regulate the charging of the voltage storage devices and the power distribution to power-consumptive components of the telephone set during on-hook and off-hook switchhook conditions. A voltage threshold detector (301) actuates a power-down of power consumptive components including the data processor (210) when the power supply voltage falls below a particular threshold value. In the meantime, power is continuously provided to certain essential components such as the volatile memory (220) of the data processor.

Abstract: In order to provide push-button telephone service to those telephone systems not equipped to respond to multifrequency dialing signals, it is necessary to convert push-button dialed digits into conventional dial pulses. A pulse train consisting of make and break intervals representing the dialed digit is electronically converted (107) into a corresponding series of make and break intervals on the telephone line (102, 103) by switching (106, 108-1, 108-2) a pulsing transistor (101) that is in series with the telephone line ON and OFF. In order to keep the pulsing transistor ON during nondialing intervals and during each make interval, and not attenuate the voice signal, the pulsing transistor is biased by an adjustable current source (105). The current needed to bias the pulsing transistor ON is linearly related to the telephone line current flowing through the emitter-collector path of the transistor, and which varies considerably from station-to-station.