Abstract: A telephone ringing circuit responds to both conventional high voltage 20Hz ringing signals and low voltage tone alerting signals. A conventional electromechanical ringer is connected across the telephone line and is responsive to high voltage 20Hz ringing signals. A high capacitance capacitor is charged by the dc voltage present on the telephone line and is discharged across the electromechanical ringer when a tone detector circuit connected across the line detects a tone alerting signal, thereby activating the electromechanical ringer.

Abstract: An arrangement for correcting errors in words read from a memory due to a bit in a word location of the memory being stuck in one of the two binary states, 0 or 1. The arrangement is used in cooperation with parity error detection arrangements which utilize more than one parity bit per word. Upon detection of a single parity failure in a word read from a selected word location in memory the complement of the data word which is indicated to contain a parity failure is placed in the selected word location; the memory is read at the selected word location and the data so obtained is placed back into the selected word location of the memory. After this step the data in the selected word location of memory comprises the complement of the correct data word and the parity bits are all the complement of the correct parity for that data word. The correct data word for use by the processor is thus generated by complementing this later received data.

Abstract: A circuit is disclosed for charging an input filter capacitance from a source of potential before a protective circuit, e.g., a fuse, is established between the source of potential and the capacitance. If the charging circuit is connected between the potential source and the substantially discharged capacitance, a small charging current will flow through a current limiting resistance. This small current will partially charge the capacitance if no faults are present. A threshold detector circuit monitors the voltage on the capacitance and for a voltage of approximately three volts or more, in the case of a twenty-four volt potential source, activates a charging transistor. The charging transistor is controlled by feedback circuitry to provide a larger but limited charging current to complete the charging to within approximately one volt of the potential of the source of potential.

Abstract: A data processing arrangement is disclosed including a central processing unit, a plurality of peripheral units coupled to a peripheral bus, a memory access controller, a first memory bus, and a second memory bus. The first memory bus serves a first plurality of memory units and the second memory bus serves a second plurality of memory units. The memory access controller selects which of the peripheral units may use the peripheral bus to access a memory bus during a particular time interval. If use of a particular memory bus is requested by a peripheral unit for an interval in which that memory bus is required by the central processing unit, the memory access controller preempts the usage of that memory bus by the peripheral unit for the interval.

Abstract: Thermal energy transfer apparatus having a controllably variable thermal conductance comprises a heat pipe having a capillary wick structure therein, a circulating supply of working fluid which is controlled by a heater, and a thermostatic heater control which is responsive to the temperature of the hot end of the heat pipe. As working fluid condenses it is removed from the heat pipe. Liquid working fluid is recirculated into the heat pipe in discrete quantities by vapor bubble injection under the control of the heater and the heater control. If no fluid is injected into the heat pipe, the thermal conductance will decrease as condensate is removed. If fluid is injected into the heat pipe, thermal conductance will increase as fluid is supplied to the heat pipe.

Abstract: A mounting block comprises a plurality of identically structured mounting cups in which are positioned alternatively a fuse support or a light emitting diode (LED) suport. Each LED is associated with a fuse to provide a visual status display of the fuse. As disclosed, the fuse elements and the LED elements are positioned in alternate of the mounting cups.

Abstract: A telephone line battery feed circuit for supplying talking current to a subscriber subset and at the same time reducing common mode interference signals. The inputs of a differential operational amplifier are coupled to a telephone line and the outputs of the differential operational amplifier are coupled to a battery feed circuit. The battery feed circuit provides talking current to the subscriber subset and the differential operational amplifier presents a high impedance between the battery and the telephone line to differential voice signals while at the same time presenting a low impedance between the telephone line and the battery for common mode interference signals thereby reducing the latter.

Abstract: A circuit for reducing transmitted and radiated impulse noise which is generated by opening and closing connections between a transmission path and a source of potential. In the case of closing such a connection a path is connected to a substantially zero potential and the potential is increased to the operating potential over a preset period of time. In the case of opening such a connection the connected potential is decreased to substantially zero over a preset period of time and the path is opened. A potential control circuit is connected between the battery side of the transmission path and the source of potential and the control thereof is coordinated with the connecting means to achieve the described sequences.

Abstract: A program controlled data processing system which comprises circuits for detecting that the processor is experiencing difficulty in executing programs, such circuits are responsive to the detection of such troubles for generating processor control signals for effecting changes in the processor configuration. These changes serve to restore the processor to an operating condition. The control signals are generated by a sequence circuit which operates independently of the ability of the processor to execute programs and independently of the operability of the processor clock circuit.

Abstract: A current limiting switching circuit which has general application and which comprises a photoresponsive semiconductor circuit activated by a light emitting diode. A semiconductor device is included for regulating the base drive of a transistor in the photoresponsive semiconductor circuit to maintain a constant collector current flow therein.