Abstract: A bilateral, low loss, wide band, switching circuit controls the transfer of a signal between two terminals. The balance points of a bilateral current gate connect to the terminals. A rectifier forward-biases the bilateral current gate when a controllable switching element forms a return path from the bilateral current gate to the rectifier. When the rectifier is energized, control circuitry closes the conductive path through the switching element to forward-bias diodes in the bilateral current gate so it operates as a modulator in which the signal to be switched is modulated onto the bias current from the rectifier.

Abstract: A line circuit for connecting a subscriber line to a telephony system that avoids the use of electro-mechanical elements such as relays. A bridge circuit includes a bilateral current gate in each of the tip and ring lines that can couple or inhibit signals from passing between the subscribed lines and the system. When the bilateral current gates are in an inhibit mode, an on-hook current source energizes the tip and ring lines. A detector senses when the subscriber goes off-hook, and also the dial pulses. After the current gate goes into a coupling mode, the on-hook current source and detector are electrically inactive, and an off-hook current source thereafter provides current to the tip and ring conductors.

Abstract: A bilateral, low loss, wide band, concentrator circuit selectively controls the transfer of a signal between one of a plurality of first terminals and a single, second terminal. The balance points of each of a plurality of bilateral current gates connect to one of the first terminals and to the second terminal. A floating power supply and selection switches selectively forward bias one of the bilateral current gates so it operates as a modulator in which the signal to be switched is modulated onto the bias current thereby to form a low-loss, wide-band path between the selected first terminal and the second terminal.

Abstract: An electronic telephone employing transmit and receive solid-state amplifiers having sufficiently low DC resistance to be biased by a DC signal over a pair of conductors with substantially less than four volts and having sufficiently high AC impedance for transmitting AC communication signals over and receiving AC communications from that pair of conductors. The amplifiers are directly coupled to the conductors, and the amplifiers include a transmitter section comprising a microphone and first solid state amplifier coupling the microphone to the pair of conductors, and a receiver section comprising a speaker and a solid state amplifier coupling the speaker to the pair of conductors. A shunt circuit is connected across the pair of conductors to adjust impedance characteristics of the telephone responsive to the available DC bias.

Abstract: An air-fuel ratio control system for an internal combustion engine utilizes an oxygen sensor to maintain a 14.5/1 air-fuel ratio at a first location in an intake manifold to an engine combustion chamber. A method and apparatus is disclosed for adding fuel and/or air to the air-fuel mixture at a second location, between the first location and the engine combustion chamber, so that the engine operates at a high economy, low emission point when idling, running at a substantially constant speed or decelerating and operates at a low economy point, yet still with low emissions, only when accelerating.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air intake connected to a burning chamber having an oxygen sensor and an intake manifold to an engine combustion chamber. Fuel is mixed with air in both the air intake and the intake manifold. The oxygen sensor maintains a 14.5/1 air-fuel ratio in the mixture in the air intake, and a pressure differential sensor equalizes the pressures in the air intake and the intake manifold. The rate of flow of fuel into the intake manifold is varied so that the engine operates at a high economy, low emission point when idling, running at a substantially constant speed or decelerating and operates at a low economy point, yet still with low emissions, only when accelerating.