Abstract: A synchronous time division digital multiplexer apparatus utilizing frequency shift keying to transmit data from a plurality of parallel input channels that are sequentially sampled and converted to serial data having non-return to zero (NRZ) characteristics. Frequency shift keying is used to modulate the obtained serial data with a sinusoidal audio carrier. Simultaneously, the system clock is automatically modulated by means of frequency shift keying with another sinusoidal audio carrier, or manually by a repetitive frame synchronization pulse. The data carrier and clock carrier are linearly combined, bandpass filtered, and level adjusted for over a voice grade transmission media.

Abstract: The invention relates to telephone transmission systems in which frequency multiplexing is carried out by digital processes. It consists in substituting to a computation step of an analytical signal a computation step of a much simpler complex signal. The ultimate signal obtained is not compatible with standard multiplexing apparatus, but may nevertheless be transmitted along ordinary channels.

Abstract: The test circuit disconnects the active elements of the coupler from the input and output and applies a test signal to the input of the active elements. The output of the active elements is first compared with a first threshold which if exceeded or equaled provides a first indication. Within a predetermined time period the output of the active elements is compared with a second threshold to determine if the control function of the active element has reduced the input to the second threshold within the time period. If this condition prevails, the indication previously provided is removed; otherwise, the indication remains and a faulty coupler is indicated.

Abstract: This invention comprises a telephone hybrid circuit having two opto-coupler arrangements for transferring voice signals from the two-wire line to a port of the switching system on one hand and from a port of the switching system to the two-wire line on the other hand. In addition, a pair of feeder circuits in the form of current sources comprising active elements are provided for feeding a constant positive direct current to one wire of the two-wire line and a negative direct current of equal magnitude to the other wire of the two-wire line. Each of the current sources includes control circuitry for maintaining a constant ratio between the current furnished by the current source and a control current common to both current sources. A control current path is connected to the output of one of the opto-coupler arrangements for generating a common control current in response to a dc signal and a superimposed voice signal received from a port of the switching system.

Abstract: An interconnect circuit arrangement for patching a simplex or half-duplex radio network into a standard telephone system. It includes means for sending beep tones to the parties at the end of each message so that they can readily recognize when each is supposed to talk. The tones are sent automatically when the party on the telephone system concludes his messages, and under manual control of the party at the radio end when he concludes his. Special access codes are provided to prevent unauthorized access to the radio system and to set the circuit for special functions. Various override features are included to facilitate operation and avoid time delays that have heretofore tended to hinder conversations in VOX simplex and half-duplex radio systems.

Abstract: Apparatus for automatically dialling telephone numbers and a card indicative of the number to be called, in which the card is provided with three tracks. The first track is a continuous rectilinear sawtooth track and the second track is parallel thereto and has formed therein cavities, the length of which are indicative of the number to be called. The third track is associated with the second track and is used to stop the card at a particular point. In the apparatus, feelers are provided to co-operate with each track and the card is pushed into the apparatus by a user and will return at a uniform speed. A first feeler can co-operate with the first track to produce a train of impulses only when a second feeler engages in a cavity of the second track, so that the length of the train of impulses is determined by the length of a cavity of the second track. These cavity lengths are indication of the number to be called.

Abstract: Apparatus for turning off power-consuming appliances in rooms of a building having a private automatic branch exchange telephone system includes computer-controlled means at the exchange central periodically to apply short bursts of audio-frequency oscillations to telephone lines going to rooms in which power can be conserved. Detecting means in each room connected to the room telephone line provide an output on receipt of a burst which operates a line relay in the room, disconnecting power from the appliance in the room, for a predetermined time period greater than the time period between the periodic application of bursts at the exchange central.

Abstract: The detection of frequency tones, such as used in telephone pushbutton dialing to identify the digits of a called number, is performed in a digital manner which affords both speed and reliability of detection, by repetitively measuring the frequency of a frequency tone so that each measured frequency can be assigned to one of a plurality of valid frequency bands, maintaining a count thereof for the individual frequency bands, and assigning the frequency tone to the first frequency band to achieve a predetermined count level.

Abstract: A duplexer coupling a subscriber line of a PCM telephone system to a modulation channel and a demodulation channel comprises a plurality of transistorized amplifier stages with input connections from the demodulation channel and output connections to the modulation channel. The modulation channel is decoupled from the demodulation channel by being connected, directly or through one such amplifier stage, to a neutral point of a resistance network inserted between the demodulation channel and a transistor connecting the latter channel to the subscriber line; the neutral point may be the junction of two resistors or the output of an operational amplifier having inverting and noninverting inputs connected to cophasally energized points of the resistance network. Each of the two channels includes a filter and an associated amplifier which may be combined into an active filter of the Tchebycheff type. In the quiescent state of the system the power supply to the active filters may be cut off.

Abstract: Disclosed is a line circuit providing the normal line circuit functions and key system control functions within an exchange using time division switching. The line circuit may be used interchangeably for key telephones or non-key telephones. In the former case, the circuit provides the well-known key telephone features for multiple line access at each station of a plurality of stations. Each line circuit provides electronic signalling controls, such as lamp flash indicating a call awaiting an answer, lamp wink indicating a line is on a hold condition, and the fully lit line busy indication, together with audible controls for a called line, and also provides an inverted flash signal at the line circuit for trouble or problem situations.

Abstract: A regulator which can be used in combination with equipment connected to a telephone type line. The regulator senses the amount of direct current being passed by the line and adjusts its internal AC impedance in inverse relationship thereto. This will shunt alternating current signals more severely when connected to short line loops having relatively small insertion loss, protecting a central office from excessive signal amplitudes.

Abstract: A time space time (TST) switch using two basic modules, a time switching module and a space switching module with individual module elements interconnectable to realize a great range of time division switch sizes and configurations. Control stores and state stores associated with respective switching elements are combined and incorporated into the time switch and space switch modules.

Abstract: Loudspeaker, in particular low-note loudspeaker, provided with a cone-shaped diaphragm having a coil form on which in addition to the voice coil is mounted a piezoelectric transducer in the form of a thin plate capable of pivotal movement. The output voltage of the transducer is degeneratively fed back to the input of an associated amplifier. The plate preferably is rectangular and suspended in rubber mounts along two opposed edges. The mounts form part of a mounting board provided with printed wiring on which an electronic transformation circuit is arranged. A shallow cup in which the mounting board is accommodated ensures that the piezoelectric plate is separated in an airtight manner from the coil form.

Abstract: A personal information system wherein an illuminated information source is viewed in a mirror located closer to the eye than the shortest focal length to present in focus a visual image to the eye so that it can be viewed unobtrusively superimposed over the existing visual scene during normal activities. In a further aspect, the invention provides reflected illuminated symbolic presentation for speech interpretation assistance.

Abstract: Disclosed is a key telephone system using a line concentrator and a form of TDM signalling. A single data and supervisory control pair of wires connects a station instrument to the system to effect all switching and supervisory controls for all lines to which the station has access, regardless of the number of these lines. Each station instrument also has a pair of speech wires which are switched within a station-line matrix under the control of a memory unit as directed by the data transmitted. Lines are grouped into groupings of up to five lines accessible to each station, there being a matrix and memory for controlling the switching of the matrix within each grouping. More than five lines may be accessible from a station instrument, such instrument having connections to multiple groups through a station circuit individual to that station. Within the system, many added features, such as speech pair security, restrictions on allowed service, and the like may be readily incorporated.