Abstract: The invention provides a combination in a SLIC for telecommunication applications of ac impedance synthesis, e.g. raising the impedance of battery feed resistances by feedback techniques; in combination with real battery feed resistors and a dc block transformer. A dc blocked transformer is coupled to line current feed resistors and a feedback loop network to synthesize the desired input impedance, such that the feedback network incorporates both positive and negative feedback. A loop stabilizing resistor is used in shunt with the dc blocked transformer secondary to reduce gain peaking and phase shift.

Abstract: An arrangement for providing a subscriber line with an operating potential. The energy to the line is transferred thereto inductively at a fixed frequency and includes the rectification means on the subscriber side of the inductor. The amount of energy transferred to the line is controlled by pulse width. The control pulse width circuit includes means to decrease the energy transfer above a level at which a subscriber station internal regulation would be defeated.

Abstract: An electronic ignition timing system for an internal combustion engine which rotates a crankshaft is disclosed. The ignition system comprises a plurality of variable engine condition sensors which produce corresponding analog output signals and a crankshaft position sensor. A timing control logic circuit periodically multiplexes each of the variable engine condition sensors such that they are sequentially connected as inputs to an analog to digital (A/D) converter which produces an output signal comprising a pulse train for each of the multiplexed engine conditions. The total number of pulses in each pulse train is related to the magnitude of the variable engine condition currently being connected to the A/D converter. In addition, high resolution crankshaft position pulses are produced, preferably by an electronic angle divider which receives coarse crankshaft position pulses and produces high resolution crankshaft position pulses.

Abstract: A digital signal processing circuit for controlling the spark timing and exhaust gas recirculation (EGR) of an internal combustion engine is disclosed herein. The circuit first samples the magnitude of the vacuum manifold pressure and produces a complex function analog output signal in response thereto. The output signal is produced by first converting the vacuum pressure to a digital signal, then using a read only memory to produce a complex function digital output signal and then reconverting the digital output signal to an analog output signal. The pressure analog output signal is then stored in a first holding device. Subsequently, an analog signal proportional to the period of engine revolution is sampled by the same circuit.

Abstract: The disclosure relates to a monitoring system and method for determining the magnitude of the equivalent voltage source impedance and the magnitude of the equivalent voltage source voltage on a telephone line and switching network of a telephone system. The monitoring system measures the Thevenin source voltage and source impedance to ground on the line by applying two independent voltage conditions to the line and senses the resulting steady state voltages thereby produced in a sensing resistor. The magnitudes of the sensed steady state voltage are thereafter utilized for obtaining the Thevenin source voltage and source impedance magnitudes.