Abstract: A connecting line is provided between a switching center and a subscriber for transmission of telecommunication signals. At the subscriber's end of the connecting line, there is located a device which, in addition to other passive and active units, includes a transformer, whose output winding is subdivided into two partial windings of identical size. A first capacitor, a switch and a second capacitor are connected in series between the partial windings. To prevent distortions of the dial pulses, a connecting line between the switch and the second capacitor is connected with a reference potential of the circuit arrangement.

Abstract: To detect tones for call progress monitoring, hysteresis apparatus is provided whereby the output of a typical tone detector such as a comparator operating in conjunction with a selective filter is monitored by a counter. The counter is incremented and decremented according to whether the input is indicative of the presence or absence of a tone. If the counter reaches a predetermined count within a given period of time, then an indication is made that the tone exists. If the counter does not reach this predetermined count or threshold within the applicable time, then it is an indication that the tone does not exist. The thresholds of the counters plus the amount by which a counter may be incremented or decremented for each input signal is variable for each tone.

Abstract: A reciprocal impedance conversion network is disclosed. Such conversion network preferably is used in a reciprocal negative impedance repeater for the nonloaded cable facilities of a telephone system. Two independent voltage sources for generating reciprocal negative impedance are connected between a first port and a second port. The first port is operably connected to the first voltage source such that a series negative impedance appears at that port. This port is specifically connected to the switching equipment of the telephone system. The second port is operably connected to the second voltage source such that a shunt negative impedance appears at that port. The second port is specifically connected to the nonloaded cable facilities of the telephone system. The network further provides a frequency dependent gain circuit which is useful for equalizing the losses along the nonloaded cable facilities.

Abstract: A unique cellular telephone (500) includes audio circuit 502, microcomputer (508), indicators (506) and (507), cellular telephone transceiver (519), and keypad controller (504) for controlling the operating modes thereof and automatically placing and receiving cellular telephone calls dialed in any pattern. The keypad includes numerical keys (0-9, # and *) and function keys (MEM and END/CLEAR) for entering digits of telephone number and key sequences for selecting operating modes. Power is applied to the cellular telephone transceiver (519) in response to concurrent activation of at least two keys. Each telephone number digit is detected and accumulated by microcomputer (508) and, after a pause of four seconds, the accumulated digits are sent via a data bus (511) to cellular telephone transceiver (519) for placing a telephone call. The call is subsequently terminated when the END key is activated or an END command is received by the cellular telephone transceiver (519).

Abstract: A control signal generator is provided to supply a control signal to a control unit of a telephone set having dial memories. Information stored in a memory in the dial memories is forbidden to be erased, unless the control signal is supplied to the control unit. As a result, important information is protected from erroneous erasing in the dial memory.

Abstract: An isolation circuit (20) that is devoid of coupling transformers and yet suitable for use as a telephone line interface. The circuit is characterized by very wide bandwidth, low noise, and high linearity. Opto-isolators couple analog transmit and receive channels in a user device (12) across an isolation barrier (57) to a line pair for full duplex communication on the line pair. The interface circuit, which also includes a hybrid (55), includes first and second oppositely directed linear optocouplers (50,52). The first is disposed between the transmit channel and the hybrid; the second between the receive channel and the hybrid.

Abstract: The present invention is directed to a telephone unit having a redial capability wherein if the number called is busy and a redialing is desirable, a determination is made as to whether a dialing operation has taken place since the telephone was placed in an "off" hook status. If no dialing operation has taken place, then the telephone will dial the desired redial number which is the last dialed telephone number. If the determination is that a dialing operation has taken place since the phone was placed in an "off" hook status, then an operation is initiated upon initiating the redial order command where the telephone is electronically placed in an "on" hook status in order to release the telephone line of the telephone network, and then is reestablished in an "off" hook status for capturing a line of the telephone network. Upon capturing a line of the telephone network, the redial system redials the desired telephone number.

Abstract: A telephone system having a dial data changeover switch transmits either a dial pulse signal or a dual-tone multifrequency signal along a telephone line. This telephone system includes a changeover switch for changing between a KEY signal from a key board and a control signal from a CPU. When a power interruption sensing device senses that the external power voltage is below a predetermined voltage, the changeover switch shunts from the control signal to the KEY signal and transmits either the DTMF signal or the DP signal along the telephone line.

Abstract: Communication equipment in which first and second telephone number data is registered by a single selection key and first and second telephone number data is selected and dialed according to selection key input includes a data communication device and a conversation communication device. A first detector detects the hook state of the conversation communication device and a second detector detects the presence or absence of data. In response to the selection key input to dial the selected telephone number, a controller selects either the first or the second telephone number data according to the operation of the first and second detectors.

Abstract: An improved noise cancelling apparatus is disclosed combining a unique directional noise cancelling microphone structure with a noise reducing, signal shaping electronic circuit. The microphone structure simultaneously receives two input signals; a first signal containing only ambient noise and a second signal containing both ambient noise and a voice signal. The microphone structure cancels the two noise components and transmits the voice signal into an electrical signal. The electronic circuit further processes the electrical signal to suppress any noise components not cancelled by the microphone structure. The electronic circuit also functions to enhance the high frequency components of the voice signal to provide a richer, more pleasant sounding output. Because the unique microphone structure is combined with the electronic circuit the noise cancelling apparatus of the present invention provides a cleaner, more pleasant sounding output than that of the prior art.

Abstract: A telephone set is disclosed which includes an adjunct interface module within the telephone set stand of the telephone set. This adjunct interface module converts the telephone set interface, which connects the telephone set to a premise switching system, to a different interface that is used by adjunct telephone equipment associated with the telephone set. Typically, the telephone set interface is a non-standard, or proprietary, interface, while the adjunct interface is the more common tip-ring interface.

Abstract: A keypad monitor which monitors the condition of a plurality of switches of a keypad is activated in response to receiving clock signals from an external clock source and is deactivated in the absence of the clock signals. The keypad monitor includes a key switch monitor which detects the closure of any one of the keypad switches to provide a first output signal, a clock detector for detecting the absence of the clock signals to provide a second output signal and any key down output logic which is responsive to the first and second output signals for providing an activation signal. The activation signal causes the external clock source to provide the keypad monitor with the clock signals for activating the keypad monitor.

Abstract: A multiple phone ring boost circuit rings multiple subscriber telephones synchronized with a ring signal sent from a telephone company central office is connected to multiple subscriber telephones. A local generator creates a local ring signal, and a local generator sensing circuit determines if the local generator is functioning properly. A ring sensing circuit senses if a ring signal is being received. A switch connects the line leads to the subscriber leads in a first position, and connects the local generator to the subscriber leads in a second position. A control circuit varies the switch between the second and first positions. When the ring sensing circuit detects an incoming ring signal and the local generator sensing circuit detects a properly functioning local generator, the switch is placed in its second position. When the ring signal pauses, the control circuit places the switch in the first position.

Abstract: A central clock unit has a ring generator for generating ringing signals and a DC voltage source for generating display signals. With the assistance of the central clock unit having a switching unit that is controlled by a central processor unit, either the ringing signals or display signals are transmitted to an analog communication terminal via a ring down line and a line connection unit. Within the line connection unit, a switch is controlled by a ringing-display procedure to generate the desired rhythm of the ringing or display signal. A read/write memory unit within an I/O device is divided into dedicated memory sections to eliminate any delays associated with the control of the ringing-display procedure. The dedicated memory sections are used to store information which is written to or read from the memory by the I/O device and the central processor unit.

Abstract: A ringing signal control circuit used in a Subscriber Line Interface Circuit (SLIC) for connecting a ringing signal bus to a subscriber loop. The ringing signal bus transmits ringing signals along the subscriber loop to a subscriber instrument. The SLIC includes a High Voltage Line Interface (HVLI) circuit connected to the subscriber loop and the ringing signal bus is connected to a ringing generator that provides a source of ringing signals. The ringing signal control circuit comprises a logic interface circuit connected via an address/data bus to a central controller that is arranged to receive ringing connection signals from the central controller and to generate a ringing activation signal. A ring timing circuit receives the ringing activation signal and generates a first and second output signals. The second output signal is transmitted from the ring timing circuit at a specific time interval subsequent to the first output signal.

Abstract: A directional microphone assembly is constructed from a first-order-gradient microphone element enclosed within a housing, molded from an acoustically-opaque, resilient material such as Ethylene-Propylene-Diene-Monomer. The microphone element includes a diaphragm which moves under the influence of sound pressures applied on its opposite surfaces to generate an electrical signal which is proportional to the differential sound pressure. The housing includes a first acoustically-transparent channel for communicating sound pressure from a first opening in the housing to one surface of the diaphragm, and a second acoustically-transparent channel for communicating sound pressure from a second opening in the housing to the other surface of the diaphragm. The housing supports the microphone element and forms a continuous seal around its perimeter so that sound pressure in one channel does not leak into the other.

Abstract: A message arrangement and method for interfacing a digital telephone Digital system including a Digital Facility Line Card (DFLC) that connects a user operated Telephone Instrument (DTI) to a stored program operated digital Central Office (CO) system. The message arrangement comprises, a DFLC message processor that generates and transmits to the DTI control messages in response to report messages transmitted by the DTI, following a user activated DTI event. The control messages provide the user with visual and aural DTI operating information. The DFLC message processor further generates and transmits to a CO system central controller, device report messages requesting access to, and network services from the CO system, responsive to call processing report messages from the DTI. The CO system central controller sends device control messages to the DFLC which operates in accordance with the received device control messages to generate and transmit to the DTI, DTI control messages.

Abstract: A telephone protector is contained within a housing having an input connection and an output connection. The protector comprises an externally accessible fuse compartment having fuse contact pairs. A removable fuse holder capable of locating a fuse within the fuse compartment is provided. A fuse holding element is disposed on the removable fuse holder capable of holding fuses with respect to the removable fuse holder and positioning the fuse in engagement with the fuse contact pairs. Strain relief means is provided to reduce strain on the wires entering the housing.

Abstract: Disclosed is a dialing apparatus used for a power failure extension telephone set 30 in a key telephone system. The power failure extension telephone set 30 is driven by power supplied from a key service unit 2 so as to function as an extension telephone set when power is supplied to the key service unit 2, but directly connected to an office telephone line 1 so as to function as an individual telephone set when power is not supplied to the key service unit 2. The dialing apparatus comprises a dial switch 31 of single contact-layer structure and a control switch circuit 21 connected to the dial switch 31 and changed over according to the power supply or power failure condition of the key service unit. That is, when power is supplied to the key service unit 2, the control switch circuit 21 connects the dial switch 31 to a control circuit 19.

Abstract: A communication system for displaying route specific messages onboard a plurality of mass transit vehicles operating along designated routes within a geographical area serviced by a cellular telephone network includes a transmitter connectable to any telephone in the telephone system, the transmitter capable of transmitting messages to any other addressable telephone number in the system, and a cellular based visual communication unit mounted onboard each of the vehicles, each of the units having an addressable telephone number. The transmitter and each cellular based visual communication unit cooperatively assure that the contents of the route specific messages transmitted from the transmitter via the cellular telephone system to the respective vehicle are received, stored and subsequently displayed in an error-free condition, regardless of whether or not the vehicles are mobile or stationary.