Abstract: A transportable telephone exchange apparatus which includes small capacity telephone exchange facilities which are divided into a plurality of containers for transportation to an installation site by boat or by vehicle, has an improved frame packing density within the frame and is constructed to facilitate maintenance.

Abstract: An essentially non-dissipative, strap-free, continuously adjustable power unit inherently impervious to shorts and open circuits for powering repeaters in a T1 or similar telephone span line is disclosed. The unit uses a pulse-width modulated inverter in the converter input circuit to produce a variable-voltage D.C. output to the span line. The pulse width or duty cycle of the inverter is controlled by a control logic which senses the span line current and maintains it at a selectable predetermined level without any apreciable power dissipation.

Abstract: The invention relates to a device for digitally detecting a frequency in a PCM signal.In accordance with the invention, an up/down counter is provided which receives a up-count pulses when there is a change of sign in the signal to be checked and which receives r down-count pulses when there is no change of sign in this signal. The numbers a and r are determined as a function of the ratio between the sampling frequency of the PCM signal and the frequency to be detected, so that it is possible to deduce the presence of this frequency from a balance between the number of up-count pulses and the number of down-count pulses.Application: detecting the neutralization tone for an echo suppressor in a PCM telephone line.

Abstract: An apparatus for blocking the transmission of echo signals in telephone communications circuits is disclosed. The apparatus employs a voice-activated switch in the transmit channel at each telephone terminal of the telephone circuit to block transmission of signals below a selectable threshold. Under all conditions where received speech signals are present at a telephone terminal, a higher threshold for the switch at that terminal is selected than would otherwise be used to block noise in the channel. This higher threshold is set above the level of the echo signals to prevent their transmission from that terminal by the switch.

Abstract: A supply arrangement for a subscriber's line circuit comprising a high frequency pulse source provided with switching means, controlled by a control generator for controlling the mark-space ratio of the high frequency pulse source. By the choice of the mark-space ratio, d.c. voltages of any desired level as well as a.c. voltages can be supplied to the subscriber's line.

Abstract: This hybrid circuit utilizes two amplifiers such as operational amplifiers without transformers. A bridge arrangement is used in which there are four impedances, the line being one impedance. One amplifier is the second amplifier which is connected across two points of the bridge as a differential amplifier. The other amplifier is the first amplifier which is connected across the other two points of the bridge. One wire of the line acts as a common point for the bridge and the amplifier system. The bridge is a balanced configuration.

Abstract: An apparatus for providing simultaneously a multiplicity of independent non-interactive effects on the transmission characteristics of a voice-frequency telephone transmission line. Output voltage and current signal processing circuitry is provided which generates voltages for insertion in series with the line and currents for insertion in shunt with the line. Input voltage and current signal processing circuitry is also provided to sense the signal voltage across and the signal current through the transmission line and to generate a multiplicity of voltages and currents which are functions of the signal voltage and the signal current as well as of the voltages and currents fed back from the output signal processing circuitry to the input signal processing circuitry. A multiplicity of line conditioning control units couple the input signal processing circuitry to the output signal processing circuitry.

Abstract: A remote gain controlled optocoupled device is disclosed utilizing a DC reference voltage in the output section to compensate for variations in the optocoupling characteristics of the circuit. The DC voltage level output of the photodetector, which is a function of the light transfer characteristics of the circuit, is compared to a remotely controlled reference DC level. The output AC signal level, which substantially tracks the DC voltage output, is gain adjusted under control of the compared DC voltage levels.

Abstract: A telephone hookswitch actuator and handset support assembly arranged to allow a telephone instrument to be used as either a desk or wall unit. The actuator is constructed of two independently pivoting members, a first hookswitch actuator member controlling the "on-hook" and "off-hook" switching and a second alternatively positionable support member. When the telephone instrument is intended to be used as a desk unit a retaining device manipulated from the exterior of the telephone is adjusted out of contact with the support member allowing the support member and actuator to act in unison. When used as a wall unit the retaining device is adjusted into contact with the support member which then retains the member outwardly extended allowing a cavity on the handset to accept the support member, supporting the handset.

Abstract: A TOUCH-TONE signal to dial pulse converter arrangement isdisclosed in a step-by-step system. The arrangement is equipped with a plurality of trunk circuits interposed between line finder and selector switches for extending calls from TT (TOUCH-TONE) telephones through a switching network to a lesser plurality of TT to DP (Dial Pulse) converters. Each of the converters is time slot connected to a common translator under control of a time slot allotter. The common translator includes a single end-of-keying control circuit having decoders, a cross-connection terminal field, a combinational logic circuit, an encoder and a comparator for cooperating with all of the converters successively in individually assigned time slots to determine when the end-of-keying occurs on each call served by the converters.

Abstract: The disclosure is directed to a calling circuit which controls the connection of two different audio signal sources to a single audio signal transmission path for broadcasting the audio signals over a telephone set loudpseaker as well as controlling the energization of indicators in the telephone set and at the main control circuit. Only four conductors are used to connect the telephone set with the main control circuit, two of which are power supply conductors which may supply other circuits as well.

Abstract: A system for transmitting data between distant locations comprises a modem at each location and a communication channel, typically a telephone line, whose transfer function has a principal component whose variation is slow and a second component whose variation is faster, but whose action is lesser. A correction device is located in the modem at the output of the channel and comprises an equalization filter constructed to compensate for the principal component and a digital adaptive network having a few coefficients and a low time constant, compatible with the frequency of the second component. The coefficients of the digital network may be adapted independently of those of the equalization filter.

Abstract: A class of electronic hybrids is disclosed in which the line balancing impedance is made frequency-sensitive in order to better match the frequency characteristic of the connected line and is made voltage-controlled in order that a single network can be used to match a variety of different gauges of telephone cable pairs. The matching impedances are synthesized utilizing RC networks and the voltage control is realized with two-node Miller effect impedance multiplication circuits realized by long-tailed pairs for synthesizing hyperbolic tangent impedance functions under the control of a voltage.

Abstract: A telephone set has a transmitter-receiver including a first portion for mounting a microphone, a second portion for mounting a speaker for loudspeaking, an earphone for low speaking with an opening formed in the first portion so that the side walls of the opening connect the microphone to the second portion without acoustic coupling between the first and second portions, and a base member shaped to support the transmitter-receiver. The base member has a telephone number operating board which is accessible through the opening in the first portion when the transmitter-receiver is positioned on the base member. A mechanical switch on the base member responds to the placement of the transmitter-receiver to effect switching between the loudspeaking and lowspeaking modes of operation. Also disclosed is a microphone support member which can support the microphone without exerting any adverse effect on the characteristics thereof.

Abstract: An improved echo suppressor for use at intermediate points in a telephone transmission facility, whereat both speech signals and single frequency signaling tones may simultaneously be present, provides voice-switched echo control without affecting network signaling. In one mode of operation, during periods of critical signaling tone transmission and while high level or augmented tone is present, such as during dial pulsing, the echo suppressor is automatically disabled and completely transparent to the tone, whereby the signaling tone may pass therethrough completely without distortion. In another mode of operation, during periods of continuous low level signaling tone, the tone is blocked from an attenuation control portion of the echo suppressor and is reinserted into the transmission facility thereafter, irrespective of the presence or absence of speech energy in the facility.

Abstract: The magnitude of current supplied to a subscriber telephone loop during both loop start and ground start modes of operation is controllably limited by employing a battery feed circuit including an adjustable line build-out impedance. Resistors are controllably switched in or out of the battery feed circuit leads as a function of the potential developed across the line build-out impedance in a predetermined one of the battery feed circuit leads. Since the line build-out impedance being adjusted in value is within the detection loop, there is hysteresis in the switch points for switching the resistors in and out of the battery feed circuit leads. This hysteresis minimizes possible oscillation at the switch points and, therefore, minimizes development of unwanted signals on the subscriber loop. The use of an adjustable line build-out impedance further allows use of small resistance value, low wattage resistors as line build-out impedance elements.

Abstract: An improved telephone connector block construction permitting the convenience of blocks normally connected at parallel sidewalls thereof to be conveniently interconnected at a forwardly facing surface in those installations where side interconnection is not practical or desirable. The construction includes an element providing guiding means for jumper connections leading to the forwardly facing surface including the necessary fanning openings, and a second element forming pin terminal means on said forwardly facing surface. The improved structure permits the mounting of adjacent connector blocks at closer intervals than otherwise possible where specific installation sites require such closer spacing.

Abstract: An intercom calling apparatus in a key telephone system including a page switch for switching the transmitter from a talking circuit network to an intercom calling path while a contemporaneous call on a central office line is held by the series combination of a resister and a varistor forming a parallel circuit with the transmitter in the talking circuit network.

Abstract: In the case where a two-wire circuit forming a trunk or a subscriber line of the two-wire system is converted by a hybrid circuit to a four-wire circuit of sending and receiving paths to form a transmission line between subscribers, if an impedance variation on the two-wire side is large, a leak from sending path to receiving path occurs and is amplified to cause singing. To eliminate the singing, a circuit for detecting the impedance fluctuation of the two-wire side is inserted in the two-wire circuit, and switching means inserted in the four-wire circuit is activated by an impedance detecting signal of the detecting circuit to electrically open the four-wire circuit, thereby preventing the singing phenomena. This method does not involve the use of an expensive attenuator which is troublesome to design for the prevention of singing.

Abstract: A class of electronic hybrids is disclosed in which the line balancing impedance is made frequency-sensitive in order to better match the frequency characteristic of the connected line and is made voltage-controlled in order that a single network can be used to match a variety of different gauges of telephone cable pairs. The matching impedances are synthesized utilizing RC networks and the voltage control is realized with two-node Miller effect impedance multiplication circuits realized by long-tailed pairs for synthesizing hyperbolic tangent impedance functions under the control of a voltage.