Abstract: According to the present invention there is provided a current detector useful in interconnection of an automatic telephone exchange with a central office via TIP and RING leads and comprising; rectifying apparatus coupled to the TIP lead for rectifying at least a portion of the current flowing therealong of either polarity; and detector apparatus receiving the rectified output of the rectifying means and providing a DC output signal indicating current passage along the TIP lead.

Abstract: A combination automobile sun visor and speaker assembly for use in automobiles and other motor vehicles, to be mounted above the windshield in place of a conventional sun visor. The speaker assembly comprises a thin, flat, bidirectional speaker enclosed within a layer of acoustically transparent material and means for mounting the speaker above the windshield. The speaker assembly provides speaker placement which is superior to prior art automobile speakers and provides speakers which may be adjusted and which do not waste interior space.

Abstract: A dial pulse detection circuit for partial correction of grossly distorted line current dial pulses, which provides square wave output signals for use by later timing detection circuitry. To detect such dial pulses, the present invention establishes an upper and a lower detection threshold. For a valid dial pulse to be detected, the line current must drop through both thresholds, and then rise again through at least the lower threshold. With the provision of a detection delay following detection of the leading edge of a dial pulse, the presence of a valid dial pulse can be registered. The present technique used in detecting the presence of dial pulses substantially reduces the chances of rejection of a valid dial pulse which has a grossly distorted waveform.

Abstract: A one-way receiving path is connected to the input side of a first phase-shift network which produces signals in phase quadrature at its output side, which is connected to the input side of a second phase-shift network which is conjugate to the first and whose output side is connected to a one-way transmitting path. A two-way transmission path and a balancing impedance are connected to the junction between the phase-shift networks. The arrangement provides a balanced or unbalanced hybrid circuit. Each phase-shift network can comprise a symmetrical polyphase network with cascaded network sections for handling voice frequency signals.

Abstract: A shoulder rest that forms an integral part of a telephone handset. The rest includes a pair of arms each pivotally connected at one end to the handset body, and a shoulder plate that is pivotally connected between the free ends of the arms. The rest approximates a parallelogram and is spring loaded so that it flips from its folded down position along the handset to its opened up position extending away from the body when a latch on the handset is released.

Abstract: In a telephone system, compensation for transmission losses over any given section of the transmission path is achieved by inserting at a selected location in the telephone transmission path a variable gain amplifying means, sensing the amplitude of a multi-frequency tone signal received from a standard multi-frequency tone sending device located at a point in the telephone transmission path distant from said selected location, said tone sending device being adapted to emit multi-frequency tone signals within the voice frequency band at a predetermined reference level, and varying the gain of said amplifying means in accordance with the difference between the amplitude of said sensed tone signal and the said predetermined reference level.

Abstract: A telephone exchange communicates with a number of scattered local stations via radio links extending from a central terminal to respective peripheral installations each comprising a radio transceiver coupled via a repeater to the line loop of an associated local station. The repeater includes a constant-current generator, combined with a polarity inverter, which is controlled via a logic network in response to signals from the exchange and from the local station (detected by a sensor in the line loop) to reverse the flow of direct current for the transmission of binary pulses to the local station. In the case of a private subscriber, these pulses may be an intermittent square wave generating a ringing signal; in the case of a public pay station they may constitute commands for the collection of tokens or coins.

Abstract: A dial pulse restorer for receiving and restoring telephone dial pulses which may be distorted, and also for discriminating telephone-hang-up pulses which may be applied to a telephone line when a remote telephone coupled to the telephone line hangs up. A particular use for such a dial pulse restorer is to control the functions of dictation apparatus operatively coupled to one end of the telephone line in response to the operation of the dial mechanism at the remote telephone. The dial pulse restorer comprises a transition pulse generator for generating transition pulses in response to telephone pulse transitions that are received over the telephone line, such telephone pulse transitions being received either in response to telephone dial pulses or to a telephone hang-up pulse. A window generator is responsive to a transition pulse to generate a window pulse of predetermined duration and substantially centered on the expected time of occurrence of the next following transition pulse.

Abstract: The invention comprises improved electroacoustic audio speaker cross-over networks. The improvements comprise both the addition of various passive elements and a novel inductively coupled circuit configuration. The improvements are applied to low pass and high pass networks and combinations thereof. In the preferred embodiments a separate electrical circuit is inductively coupled to the filter network. The physical configuration of the separate circuit can be easily adjusted to counter variations in individual speaker performance parameters. Thus, production variations in speakers from the same manufacturer or among the products of different manufacturers can be overcome and a better matching of speakers provided.In the simplest embodiment the separate inductively coupled circuit comprises a copper ring placed within an inductive coil of the filter. Adjustment is accomplished by adjusting the physical location within the coil or by small changes in the physical dimensions of the ring.

Abstract: The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a larger plurality of subscriber loops.

Abstract: Circuit apparatus for supplying a regulated loop current to a two conductor loop telephone line includes first and second line feed resistances, each having one terminal connected to a respective terminal of the telephone line. A differential amplifier has one input connected to the first resistance and a second input connected to the second resistance in common with the resistance connections to the telephone line terminals. One of the resistances has its other terminal connected to the output of an active circuit means, which circuit operates in a feedback path to supply the desired loop current to the line resistance and therefore the telephone line. The input control signal for the active feedback circuit is derived from summing the output signal from the differential amplifier with a reference signal whose magnitude varies according to the length of the telephone line.

Abstract: A transmission arrangement for use in a customer premises communication system is operable for controlling transmission during the MF digit signaling interval in situations where it is necessary to convert station dialed MF signals to pulsed digit signaling. In systems where the signaling station, the MF to dial pulse converter and the Central Office or PBX line are bridged on the same communication link it is possible for the station's MF signals to be detected by the MF receiver in the Central Office, thereby causing errors in the received digits. These problems are eliminated by inserting two transmission gates in the four-wire portion of the CO line. The gates are controlled by the processor in the customer premises communication system such that the outward gate is opened immediately upon seizure of the line by the calling station and remains open during the entire dialing interval.

Abstract: A circuit closes a remote feed loop of a series-supplied repeater in a communications channel, in the event of an interruption in the transmission line, by means of a relay which senses an interruption in the feed current to close a shunt circuit. The shunt circuit includes a resistance which is initially high, to promote rapid restoration of the communications circuit, and afterwards is lowered to minimize losses and to promote personal safety.

Abstract: A PABX control circuitry housing which functions both as a housing for the circuitry and also as an indicator console, and can be mounted either on a wall or a desk top. To achieve a narrow, inobtrusive cabinet which can be used in this way, printed circuit boards are mounted parallel to the front of the housing. Indicators such as light emitting diodes (LEDs) are mounted along one edge of each of the printed circuit boards retained within the housing. The printed circuit boards are retained on successively stepped ledges, which causes the edges containing the LEDs on each of the boards to be visible from the front of the housing. A darkened, preferably translucent window in the housing allows the operator to view the LEDs. A silk screened or other imprint on the window provides the operator an indication of the meaning of the lit LEDs.

Abstract: Equipment without telephone transformer or amplifier.It is connected to the subscriber by terminals (1, 2) and to the telephone exchange by terminals (3, 4, 5, 6). It comprises a d.c. voltage source (8), four transistors (10, 12, 14, 16) and three pairs of equal resistors (9-11, 13-15 and 17-18). Sidetone is eliminated by the circuit (18-16-17).Of use in telephone exchanges of all kinds.

Abstract: A loudspeaker protection circuit senses an overload condition caused by an improper input signal or a fault within the amplifier by sensing a DC or infrasonic signal applied to the loudspeaker. The time between zero (axis) crossings of the amplifier output signal, which are related to the lower frequency components of the signal, are detected. If the period of time between zero crossings exceeds a predetermined time limit, the supply of the amplifier output signal to the loudspeaker is interrupted. In order to prevent false tripping of the circuit by normal conditions, the circuit only responds to signals exceeding a predetermined voltage level.

Abstract: Hybrid circuit for transition between two-wire and four-wire lines includes first and second operational amplifiers each having an inverted and non-inverted input and output, a voltage divider connected to each of the inverted inputs, a bidirectional terminal connecting the two-wire side to the non-inverted input of the first amplifier and a transmit terminal connecting the four-wire side to the non-inverted input of the second amplifier, to feed audio voltage to the non-inverted inputs, the voltage dividers having equal resistances, a receive terminal for connecting the four-wire side to the output of the first amplifier, matching impedances connected to the non-inverted input of the second amplifier and the output of the first amplifier, the matching impedances and an impedance balancing the impedance of the two-wire side compared to input impedances to the hybrid circuit being such that, for an incoming transmission, half of the output voltage of the second amplifier is at the non-inverted input of the fir

Abstract: A direct coupled transformerless hybrid including a plurality of current mirror circuits for providing signal conversion between a balanced bidirectional transmission path and a pair of unbalanced unidirectional transmission paths. Means are provided for increasing the DC feed resistance in response to loop faults such as grounding of the ring terminal. This is accomplished by sourcing additional current into the ring and tip terminal termination resistors to reduce their equivalent impedance during normal operation.

Abstract: The balancing network is disclosed for use in a circuit for connecting a two-wire subscriber's line to a four-wire transmission line which automatically matches the impedance of the subscriber's line by utilizing the direct current flowing in the subscriber's line.

Abstract: A modular telephone jack has a plurality of cantilever spring wire contact members extending down from a top part into an aperture which receives a modular plug. Instead of being positioned in holes extending through the top part, being then bent down and then back, the contact members are molded in at one end into the top part. This avoids bending of the wire, with possible cracking of corrosion preventive plating and also reduces the amount of wire. As an additional feature the jack may be of two parts, slid together and held together at front end by interengaging formations, with one or more resilient members engaged in detents at the rear ends.