Abstract: A loop extender is used in conjunction with a pair of telephone lines extending from a telephone central office to a subscriber location in order to insert a booster DC potential on the telephone lines in such a manner as to aid the flow of DC current produced on the telephone lines by a telephone central office battery. A control circuit has one input terminal coupled to one of the telephone lines and a reference terminal, another input terminal coupled to the other telephone line and the reference terminal, and an output terminal coupled to a relay. Whenever the input terminals are supplied with a specified potential from the telephone lines, an output from the output terminal maintains the relay in a nonenergized condition so that contacts controlled by the relay couple a DC booster power supply in series relationship with one of the telephone lines.

Abstract: An elongated manually manipulable housing contains a photocell at one end for sensing energy levels in the visible frequency spectrum causing said photocell to correspondingly change in electrical conductivity. A portable power source in the housing is coupled to the photocell to provide an electrical signal corresponding to the change in the photocell conductivity. A comparator circuit in the housing compares that signal with an adjustable reference signal to provide an output signal upon a predetermined ratio between the compared signals. A multivibrator circuit in said housing is coupled to said comparator circuit and to a vibration-generating means which produces signals preferably in the audible range, so that upon the occurrence of an output signal, a user discernible, either audible or tactile, vibratory signal is generated.

Abstract: The present invention relates to a DC signaling circuit operatively associated with a communication system having an isolation transformer interconnected between a central communication exchange center and a station site such as a power substation or generating plant where high voltage potential exists. The isolation transformer provides protection from fault conditions that could apply hazardous voltage to a cable pair entering the station. Because of the presence of the isolation transformer, there is no direct path for DC signal functions to pass from the station to the central communication exchange center. Thus, the DC signaling circuit of the present invention is designed to simulate and transfer the simulated DC signals across the isolation transformer to a line side of the communication system leading to the central communication exchange center.

Abstract: A multiple circuit interrupter, designed to facilitate the selective insertion of testers and other ancillary equipment into lines of a telecommunication system, comprises a body of generally rectangular outline which is receivable in a distribution frame and is split longitudinally into a central section and two lateral sections forming two rows of jacks between them. The jacks are arrayed in a plurality of groups accommodated in respective bosses of the split body projecting from a common base, each boss being engageable by a complementary socket containing a corresponding group of plugs. The bosses and the sockets are asymmetrically profiled to insure proper alignment of the jacks and the plugs.

Abstract: An interface unit for a four wire telephone circuit includes an echo suppressor. A filter circuit is connected to the transmit line drop side to detect voice and SF signals and to selectively couple a regenerated SF signal and the voice signal to the line side of the transmit line. A passive filter is selectively coupled to the receive side to attentuate voice echo but bypass SF signals.

Abstract: An active hybrid circuit equipped with a resistor bridge, balance network and transmit and receive amplifiers for 2-wire to 4-wire long haul trunk communication between a telephone central office and a distantly located operator console is disclosed. High impedance current sources having voltage follower operational amplifiers are integrated into the hybrid for reducing hybrid bridge loading on the bidirectional 2-wire path while providing adjustable levels of transmission in all directions. One of the high impedance sources is responsive to signals received from the receive amplifier via a bridge resistor for generating output currents to produce desired levels of the received signal on the 2-wire bidirectional path.

Abstract: A telephone station repeater is disclosed which will provide bidirectional gain in a long telephone loop at the customer's station. The repeater is powered from the central office battery over the loop and provides gain with very small power consumption and virtually no power consumption when not in use.The station repeater comprises a negative impedance amplifier including a shunt negative impedance, a series negative impedance and an autotransformer connected in a .pi. configuration. The shunt converter is disconnected when the telephone set is on-hook. The autotransformer provides impedance matching to the telephone set.

Abstract: A repeater suitable for use in submerged signal transmission systems, the repeater having inherent protection against power surges. The repeater includes a signal path including an amplifier and a separate path for powering the amplifier. The power path includes a zener diode and gas discharge tubes. One or more tubes are connected to conduct on a power surge to reverse bias the zener diode and effectively switch the diode off to protect the circuit during the incidence of the power surge.

Abstract: This autobalance hybrid circuit is used to connect a 2-wire duplex telephone line to a 4-wire line which has separate receive and transmit pairs. The impedance of a balancing network automatically is adjusted to equal the impedance of the 2-wire line, thereby maximizing echo return loss. "Howling" and "singing" are eliminated, regardless of changes in the 2-wire line impedance. Balancing is achieved by comparing the absolute values of the receive line audio voltage components appearing across two coupling transformers, one associated with the 2-wire line and the other with the balancing network. A control signal, indicative of the difference between these components, alters the balancing network impedance until equal voltages are achieved. In this condition, the receive signal cancels out as a common mode in the output circuit, so that none of the receive line audio is returned to the transmit pair.

Abstract: The invention relates to a fastening arrangement in a telephone instrument of the one-piece type for both the earphone capsule and the cap which cap should be fastened to the casing in order to cover the opening of the head part. The arrangement has two elements. The first element is a body which is secured to the inside of the casing in the top of the head part, and two oppositely directed tongue-formed parts. The first part, directed upwards, engages an upper collar-formed socket on the inside of the instrument cap and the second tongue-formed part contacts the upper front surface of the earphone capsule. The second element is a body with a rear projection engaging an aperture of a printed circuit card mounted inside the throat of the casing and two oppositely directed tongue-formed parts. The first of these parts contacts the lower front surface of the earphone capsule and the second engages a lower collar-formed socket on the inside of the instrument cap.

Abstract: After description of a number of prior art automatic telephone number identification systems and certain problems associated therewith, a new method and apparatus for use in such systems which overcomes the problems of the prior art is described. In its preferred form, the method includes the steps of applying to the telephone line at a central office a voltage which has a magnitude sufficient to produce a first predetermined value of loop current in the telephone line. At each party station, the loop current is caused to change between the first predetermined value and a second predetermined value in a manner unique to that party station, with the second predetermined value being smaller than the first predetermined value but greater than a value of loop current that would signify to the central office that an on-hook condition exists on the telephone line.

Abstract: A remote power supply system is disclosed which is particularly for monocial transmission lines equipped with repeaters. It comprises at least one current transformer inserted between two sections of line in a local power supply circuit at each repeater. The transformer has two identical primary windings one inserted in a first branch connection connecting the inner conductor of a line section to the outer conductor of the other line section, the other inserted in a second branch circuit connecting the other conductors of the line sections.

Abstract: Magnetic flux generated in a core of a transformer employed in a transmission network by subscriber loop direct current is compensated by controllably generating a current to induce a magnetic flux equal and oppositely phased to that induced by the loop current. This is achieved without need for an additional transformer winding other than the normal coupling windings by employing a current sensing element in circuit with the normal primary transformer winding which is effectively electrically isolated from a controllable current source connected in circuit with the normal secondary winding. The magnitude of the compensation current supplied to the secondary winding is controlled via the primary current sensing element. Negative feedback enhances the stability and linearity over a desired current range. Isolation between the primary and secondary circuits is realized by employing optical isolators, each including a light emitting diode and associated phototransistor.

Abstract: A circuit is provided for improving the manner in which tone signaling-to-dial pulse converters interface with prior art dial pulse registers. Instead of allowing the converter to operate the register's line supervisory relay, the converter directly operates the dial pulse counting relays of the register. In this way, changes in battery and ground potential and impedance which may be noticeable each time the conversion apparatus pulses the line relay are eliminated, and the line relay in the register is allowed, uninterruptedly, to supply battery and ground to the multifrequency signaling station throughout the duration of signaling. The direct operation of the pulse counting relays permits faster pulsing speeds because neither the distributed capacitance of the line nor the lumped capacitors used in connection with the line relay are in the pulsing path.

Abstract: A line card circuit providing supervisory functions in a key telephone system is disclosed. Two multi-contact relays perform all of the switching functions required to operate the audible and visual signaling devices used to indicate incoming calls, busy lines, and held calls, and to switch a shunt impedance across the line conductors to maintain line current when a call on that line is being held. Ringing voltage and line current are sensed by semiconductors which comprise the combination of light-emitting diodes and an adjacent light-responsive semiconductor switch. These optical semiconductors are interconnected with other semiconductor devices to form a logic circuit for actuating the two control relays, and for disabling the line current detection circuit when the associated line is being held.

Abstract: A key telephone system, in which at least one CO line, at least one intercomm. line and control lines are arranged between a key service unit and a plurality of key telephone sets. The key service unit is provided with a scanning circuit for generating multiplexed code units indicating the connection state of each channel of said CO line and said intercomm. line in a time-division manner to scan the key telephone sets. The key service unit further includes means for transmitting the code unit to each key telephone set through said control lines. Each of the key telephone sets includes a decoder for decoding the code units thus transmitted to obtain individual indication signals indicating the states of each channel.

Abstract: The electrical signals generated by an audio source are applied to a plurality of series connected light emitting diodes which are illuminated responsive to the signals. The light emitting diodes are respectively optically coupled to individual phototransistors, each of which is connected in series with a resistor across the hold impedances of the hold circuit of an individual telephone line. When one of the hold impedances is connected across its associated telephone line, line current flows through the hold impedances. Line current also flows through the parallel resistor when the phototransistor is turned on responsive to the illumination of its associated light emitting diode. The phototransistor thus modulates the current flow through the hold impedances to provide an audio signal output on the held line.

Abstract: A multi-channel digital echo suppressor wherein analog signals on a plurality of paired transmit and receive lines are sampled and digitized to form an interleaved sequence of parallel digital words. The interleaved digital words are accumulated for a predetermined period to form accumulated sample sums in sequence for each of the respective transmit and receive lines. Means are provided for segregating the receive channel accumulated samples from the transmit channel accumulated samples and bringing the samples for the respective channel pairs back into time correlation. The receive line accumulated samples are sequentially compared against a predetermined reference for producing suppression control signals which are routed to respective suppression controllers for the various channels.

Abstract: A telephone station set interface circuit is disclosed which enables a conventional nonkey telephone station set to be used in place of an electronic key telephone station set for those subscribers in an electronic business communication system requiring only a call origination and a call reception capability.

Abstract: The disclosure relates to a dial impulse relay circuit including a three-winding relay which repeats a pulse train generated by a first circuit onto a second circuit with substantially no pulse ratio distortion.