Abstract: A drive belt, such as a toothed belt such as for an automotive or other engine timing belt or a V-belt for driving machinery comprises a belt with a thin conductive wire or strip embedded in the belt material in the form of a closed loop. Such a wire tends to exhibit damage typically some time before belt failure is imminent. First and second coils are coupled by mutual inductance to the closed loop formed by embedded wire which functions as a link coupling between the first and second coils. In one embodiment, an ac current is passed through the first coil and the current in the second coil is monitored for a drop in amplitude when the embedded wire is broken and the closed loop is interrupted.

Abstract: Apparatus for monitoring a change of condition in a drive belt, such as timing belt, includes a first inductance coil, a second inductance coil, and an electrically conductive loop embedded in the drive belt. Such a conductive wire or strip embedded in the belt material in the form of a closed loop tends to exhibit damage typically some time before belt failure is imminent. The conductive loop forms a mutual inductive link coupling between the first and second inductance coils. An amplifier has an input coupled to the first coil and an output coupled to the second coil poled for causing oscillation and a detector detects change in the oscillation.

Abstract: A keyboard apparatus has keys for operation by a user. The keyboard includes a first plurality of keys being coupled to electrical generator apparatus for generating electricity from their operation. A second plurality of the keys is not coupled to electrical generator apparatus. The first plurality of keys exhibits a greater average statistical frequency of usage per key than does the second plurality.

Abstract: A keyboard apparatus has keys for operation by a user. The keyboard includes a first plurality of keys being coupled to electrical generator apparatus for generating electricity from their operation. A second plurality of the keys is not coupled to electrical generator apparatus. The first plurality of keys exhibits a greater average statistical frequency of usage per key than does the second plurality.

Abstract: A sensing coil is mutually inductively coupled with the coil formed by a wire loop embedded in a belt, as in a timing belt as for a camshaft drive in an internal combustion engine. When the embedded wire loop breaks, a circuit senses the change in impedance in the sensing coil and operates an alarm. The method is non-contacting with the belt and requires no sliding contacts.

Abstract: A timing belt system for an engine includes a first timing belt coupling the camshaft to the crankshaft and a parallel second timing belt coupling the camshaft to the crankshaft. A belt sensor provides an alarm signal upon failure of either timing belt. While the other belt continues to function and thereby prevents damage to the engine from occurring, the alarm signal alerts the operator that a broken belt should be replaced.

Abstract: An electronic circuit arrangement automatically provides an energizing current to a solenoid for ejecting a plug from an outlet coupled to a source of supply voltage upon substantial cessation of current flow being drawn by an appliance by way of the plug while the supply voltage is present. The energizing current is controlled by a controlled switching device. An optional keyed plug is utilizable for selectively enabling operation of the solenoid.

Abstract: A current amplifier has its input terminal connected to the collector electrode of its master transistor by the forward-biased emitter-base junction of a complementary conductivity input transistor. This input transistor has its collector electrode connected with potential offset to the base electrode of the master transistor. The complementary conductivity transistor tends to operate in saturation, completing a collector-to-base feedback connection for the master transistor that regulates its emitter-to-base potential to its collector-to-emitter path to conduct substantially all the applied input current. A similar emitter-to-base potential is applied to a slave transistor having its collector electrode connected to the output terminal of the current amplifier and demanding a collector current as output current proportionally related to the input current.

Abstract: In a current mirror amplifier having master and slave transistors, the master transistor is selectively provided with collector-to-base feedback to regulate its emitter-to-base potential and that of the slave transistor, the regulation of the emitter-to-base potentials conditioning the master transistor to accept input current applied to its collector-to-emitter path and conditioning the slave transistor to conduct a proportionally related output current. The selective collector-to-base feedback connection herein includes a regenerative latch circuit formed by connections between third and fourth transistors of respective conductivity tapes like and opposite to that of the master transistor. The third and fourth transistors have their emitter electrodes connected to the base and collector, respectively, of the master transistor and each has its collector electrode connected to the base electrode of each other to form the regenerative latch circuit.

Abstract: Ground fault detection apparatus improved to include detector circuiry for providing an output current responsive to imbalance in the alternating currents flowing to and from a load only if it be of sustained character and of sufficient amplitude. The detector circuitry discriminates against responses to imbalance current primarily consisting of infrequent short-duration high-amplitude spikes characteristic of transient disturbances in favor of responses primarily consisting of the sustained, relatively long-duration rectified sinusoidal waveforms characteristic of ground fault conditions, even where the average level of the transient disturbance component of the imbalance current is equal to or in excess of the average level of ground fault component.

Abstract: A regulated voltage supply comprising a degenerative feedback loop in which an amplified error signal provides either series-regulation or shunt-regulation of the output voltage. A negative-temperature-coefficient a forward-biased semiconductor junction is compared against a portion of the output voltage to develop the error signal. The comparison between these voltages is made in an unbalanced different-input amplifier configuration that provides a zero-valued error signal so long as there is a positive-temperature-coefficient potential difference between the voltages being compared. The output voltage is proportional to the sum of the negative- and positive-temperature-coefficient voltages and can be made temperature-independent by properly proportioning the summed voltages.

Abstract: A circuit for producing a band-gap reference voltage comprising first and second current amplifiers connected in a regenerative feedback loop and which includes a starting circuit. The latter initiates current flow in the loop and is automatically disconnected from the loop once the circuit output voltage reaches the band-gap value.

Abstract: A current mirror amplifier in which the potentials appearing across the principal conduction paths of its master and slave transistors are maintained substantially the same. This is done by a differential-input, single-ended output amplifier, which is connected as a non-inverting amplifier in the direct-coupled feedback connection that conditions the master transistor to conduct applied input current via its principal conduction path.

Abstract: A first junction transistor, the emitter-to-base potential (V.sub.BE) of which determines the negative-temperature-coefficient component of the standard voltage, is provided with direct-coupled collector-to-base feedback for adjusting its V.sub.BE to condition the transistor to conduct, as collector current, substantially all of an applied current that is temperature-independent or varies linearly with temperature. The positive-temperature-coefficient component of the standard voltage is developed as the difference between the offset potentials of a pair of semiconductor junctions, one of which may be the base-emitter junction of the first transistor. The negative- and positive-temperature-coefficient potentials are linearly combined to provide the standard voltage.

Abstract: A positive-temperature-coefficient difference between the emitter-to-base potentials of two transistors in particular configuration is scaled up and added to one of the emitter-to-base potentials to develop a potential, a multiple of which is supplied as the reference potential.

Abstract: A positive-temperature-coefficient potential is developed by scaling up from the potential difference appearing between the base electrodes of two transistors with interconnected emitter electrodes constrained by a positive feedback loop to operate with different densities of current flow through their respective base-emitter junctions. This positive-temperature-coefficient potential is added to a negative-temperature-coefficient potential derived from the base-emitter offset potential of one of the transistors, to provide the reference potential.

Abstract: The difference between the base potentials of a pair of transistors, which are interconnected at their emitter electrodes and operated with different densities of current flow through their base-emitter junctions, is scaled up by a fixed ratio and applied between the base electrodes of another pair of transistors with interconnected emitter electrodes to cause their collector currents to flow in a desired ratio.

Abstract: Current-mode OR gates useful, for example, in telephone cross-point switch systems. A current-mode OR gate withdraws an output current of predetermined level at its output terminal whenever an input current of sufficient level is applied to one or more of its plurality of input terminals. Each input terminal is connected to the base electrode of a transistor, having its collector electrode connected to the output terminal and having its emitter electrode connected by a resistor to a common terminal. Each input current will bias the transistor to which base it is applied, into conduction, to cause its collector current to be withdrawn through the output terminal. The total output current is constrained to the predetermined level by sensing the potential across the resistor and, in response to this potential reaching a predetermined value, clamping each of the input terminals receiving current to prevent further increase of the potential across the resistor.

Abstract: An input signal activates a current source for charging a capacitor. A first switch is closed and a memory element is subsequently SET as the capacitor voltage increases. When SET, the memory element closes a second switch and reverses the charging current whereupon the first switch is subsequently opened. The memory element is RESET upon termination of the input signal whereupon the cycle may be repeated. The switches may be connected in series for providing an output indication during the period both are closed.

Abstract: A signal to be switched is applied across the conduction path of a thyristor and a trigger signal is applied to the thyristor gate electrode. False triggering, due to transients in either signal, is prevented by a current amplifier connected at the output thereof to the gate electrode and at the input thereof, via separate alternating current conductive paths, to the gate electrode and to one end of the thyristor conduction path.