Abstract: The switching unit comprises for two-way transmission two branches, each of which includes in series an input mixer, a channel filter and an output mixer, and two variable frequency digitally controlled carrier current generators, the first of which feeds the input mixer of the first branch and the output mixer of the second branch, and the other of which feeds the output mixer of the first branch and the input mixer of the second branch. In a switching arrangement using such units, a telephone channel can be transferred from an incoming multiplexed group to an outgoing multiplexed group by means of two units whose second generators receive a common frequency, while their first generators respectively receive frequencies corresponding to the positions of the considered channel in the incoming and outgoing groups respectively.

Abstract: A chair or bed consists of a base structure forming a closed, external housing and a body-supporting means which cooperates with the housing to provide a chamber which is closed but for pressure relief openings. One or more loudspeakers is mounted in the chamber facing the body-supporting means, and each speaker is operatively connected to an amplifier so that it may produce vibrations within the chamber which are in the audible frequency range, and which are transmitted through the body-supporting means to an occupant thereof. The amplifier is of standard type which functions either with a radio receiver or with a phonograph, and which has a volume control for varying the intensity of the vibrations and tone controls for varying the output as between bass and treble.

Abstract: A method of providing a multi-port conference circuit for use in a telephone switching system employing pulse coded modulated signals for transmission and supervision. Samplings of coded information are employed as a source of conference data and comparison with the digital information contained therein is employed to choose the speaker in a conference group.

Abstract: An automatic meter-reading system monitors broadly distributed utility meters over a communication link by indirectly measuring the resistance value representative of the digit shown on the meter from calculation using the equation derived from the theory of four-terminal network. Based on the similar principle, an automatic remote controlling system monitors the answer-back signal representative of the condition of the controlled equipment at a remote station. Similarly, an automatic meter-reading system monitors a telephone subscriber's telephone call meter centrally located in a telephone exchange office.

Abstract: A wired logic PBX switching system is disclosed in which a camp-on circuit is used to provide automated call hold service. A station user places an existing call on hold by flashing the station switchhook contacts and dialing a predetermined code. The dialing of the code disconnects the station from the first call and places the trunk circuit serving the first call on hold. A second call may then be placed from the station. Upon termination of the second call, the hold condition is removed from the trunk circuit and a connection is reestablished from the trunk circuit to the station.

Abstract: A telephone line reported by a subscriber to be busy may be checked by the disclosed apparatus to determine if the telephone is actually in use or merely appears busy because of leakage in the telephone line or of the receiver being accidentally off-hook. When the telephone is actually in use, peaks in signals present on the line are counted and cause an in-use indication. When an accidentally off-hook or leakage condition is present, particular signals on the line or the absence of signals cause a not-in-use indication.

Abstract: A telephone answering service console for use in an answering service system accepting incoming calls through a pair of standard telephone lines provided with "call forwarding" and "call waiting" service is described. The console has a desk level main deck which supports control panels and a numerical directory of subscriber accounts, before which the console operator is stationed, and a directory deck in spaced, parallel relation above the main deck supporting thereupon a plurality of arcuately arranged, upstanding subscriber account alphabetical listing directory board, the console further comprising a plurality of upstanding rows of message racks, one for each subscriber account, arcuately arranged between the main and directory decks.

Abstract: An automatic H-register clear system for the prevention of erroneous convolution in adaptive digital echo cancellers is disclosed. Incoming signals from the H-register are accumulated and compared to a predetermined threshold value and when the value is exceeded, the H-register is cleared with the occurrence of the internal housekeeping cycle of the echo canceller. The clearing of the H-register allows a new impulse response model to be generated from new sampled data. In one embodiment using analog implementation, the accumulation takes place using a sequence of signal processing of digital-to-analog conversion, full wave rectification followed by integration of the signal. In another preferred embodiment using a counter detection system, each word is compared to a threshold and if this value is exceeded, a counter is indexed. If the value of the count in the counter exceeds a predetermined number during the sampling interval, the H-register is cleared.

Abstract: A converter, for converting a dual-tone multi-frequency (DTMF) signal produced by a TOUCH-TONE telephone to a 2-out-of-7 coded representation of the "dialed" number, includes an oscillator having a frequency much higher than the frequencies of the tones, a high band circuit for high band tone frequencies, and a low band circuit for low band tone frequencies. Each circuit includes a filter for passing the respective band of tone frequencies from an input terminal, a limiter for translating a received tone sine wave passed by the filter to a corresponding square wave, a counter, a switch enabled by the square wave output of the limiter for coupling the output of the oscillator to the input of the counter during a cycle of the square wave from the limiter, and a decoder for translating the resulting count in the counter to a signal on an output line representing one of the tone frequencies.

Abstract: An apparatus which modifies sound by introducing selected levels of clipping, sustaining, tone generation, echo effects, phasing effects, and suppression of low and high frequency signals to the input to a conventional audio amplifier thereby producing pleasing and interesting sound.

Abstract: A stereo speaker system for portable use having two loud speakers mounted side by side in a common housing which may be divided. The housing substantially surrounds the speakers and the speakers substantially occupy the chamber defined by the housing. The chamber has two ducts for directing the sound produced toward the listener's ears. These ducts open into the speaker chamber adjacent the speakers.

Abstract: A light weight operator's headset includes a generally cylindrical housing in which is disposed a receiver transducer, and an arm pivotally joined to one end of the housing. Secured to the arm is a microphone transducer, from which a sound conductive tube extends in a pivotally and extensibly adjustable fashion to the operator's mouth. An arcuate resilient member extends obliquely from the housing to define a slot therebetween in which the outer ear is received to thereby support the headset. A channel in the arcuate member receives the conductors which extend to their respective transducers.

Abstract: A circuit for suppressing noise pulses generated by the transfer of a charged telephone line from one supervisory circuit to another is provided. A capacitor is first connected to the telephone line and is charged to the voltage level appearing across the telephone line at the one supervisory circuit. The telephone line is then transferred from the one supervisory circuit to the other supervisory circuit and the capacitor is disconnected from across the line.

Abstract: A parity checking circuit for use in multifrequency tone receivers is disclosed wherein associated receivers are made less susceptible to digit simulation when talking is present, by verifying that the same two tones are present for the entire parity timing period.

Abstract: A guard circuit is designed to be inserted in a two wire trunk between a central office and customer terminal equipment for the purpose of reducing the time period that the customer terminal equipment, for example, a private automatic branch exchange (PABX), is subject to glare. Essentially, the guard circuit monitors the various potentials of the two wire trunk from the central office. Upon release of an established connection from the central office, ground is removed from the positive line and negative potential is applied to the negative line. The guard circuit recognizes this change in potential and separates the customer terminal equipment from the central office until the customer terminal equipment is released and reconditioned. Glare cannot occur during the separation interval and thus the time period during which glare could occur is substantially reduced.

Abstract: A communications multiplexer module (CMM) used to provide an interface between a plurality of line adapters and a host computer. A control memory is provided for storing control words, one word for each adapter. A scanner scans the adapters and at the same time addresses the memory to read out the control word associated with that adapter. The control word contains a bit or bits for designating whether the multiplexer is to operate in an input or an output mode for that adapter. Data bits are received from the line adapters serial by bits are assembled in an assembly/disassembly area of the control word. After each character is assembled it is transferred to the host computer interface. Common multiplexed circuitry is provided for performing parity checking, longitudinal redundancy checking and cyclic redundancy checking of messages.

Abstract: A single channel carrier system for telephone service is disclosed including a remote terminal having a battery charger for charging a battery during idle periods to power the remote carrier electronics. The remote electronics include a ringing generator and supervisory circuits to implement normal telephone supervision over the carrier channel.The ringing generator is a DC-to-DC converter for stepping the battery voltage up to ringing voltage level. This high unipolar ringing voltage is then interrupted at a 20 Hz rate during the ringing portion of the ringing cycle. Simple diodes serve to isolate the unipolar ringing signals from other portions of the circuit.

Abstract: Apparatus for interconnecting a time-division multiplex carrier system, such as T1, with a frequency-division multiplex carrier system, such as LMX-3. The interconnexion is effected in an all digital manner by the use of digital filters, thus avoiding the necessity of down-converting either system to voiceband.

Abstract: An automatic dial system for a subscriber telephone utilizes a keyboard array to enter coded information into an integrated circuit digit processor. The digit processor includes a programmed ROM for storing an instruction set to control the operation of the dial system, an arithmetic/logic unit for performing arithmetic and logic operations on data according to said instruction set, and a first read/write RAM for storing the data being processed.A pulse generator is selectively connected at the output of the digit processor for the selective transmission of pulse signals over the telephone lines according to the stored instruction set and coded information derived from the keyboard.

Abstract: An automatic dial for a subscriber telephone utilizes a keyboard array to enter coded information into an integrated circuit digit processor. The digit processor includes a programmed ROM for storing an instruction set to control the operation of the dial, an arithmetic/logic unit for performing arithmetic and logic operations on data according to said instruction set, and a first read/write RAM for storing the data being processed. A second integrated circuit RAM, which is selectively connected to the output of the digit processor, is provided for the storage and retrieval of changeable groups of selected telephone numbers. A pulse or tone generator is also selectively connected at the output of the digit processor for the selective transmission of pulse or tone signals over the telephone lines according to the stored instruction set and coded information derived from the keyboard.