Abstract: Existing automatic log on/log off systems in telephone systems determine whether or not a workstation is occupied, and that calls can be directed to that workstation, by determining whether or not the amplifier that provides the interface between the telephone system and the occupant's headset is plugged into the workstation. Recent headsets have a connector in the cord between the headset and the amplifier. This enables the occupant to leave the workstation without unplugging the amplifier, which defeats sensing mechanism of the existing automatic log on/log off system. An amplifier according to the invention replaces the existing amplifier and includes a detector that determines whether the headset is connected to the amplifier, and an activator that activates the existing automatic log on/log off system in the telephone system.

Abstract: A telephone apparatus has a human body approach sensor for sensing, for example, infrared rays from a human body to produce an approach signal in response to which a controller activates a lamp to illuminate, for example, a ten-key device on the telephone, thereby facilitating the use of the telephone in darkness. When the sensor operation is continued longer than a predetermined period, the controller automatically triggers an automatic dialing function of the telephone.

Abstract: An apparatus for emergency dialing and oneway communication by telephone includes an autodialing circuit for dialing a preselected emergency telephone number. The circuit is activated by a switch and provides communication of audio information from the vicinity of the device to an emergency services operator during an emergency situation such as a criminal assault of a convenience store. The apparatus is characterized by the presence of a microphone, and the absence of a speaker connection for transmitting the voice of the emergency services operator. In this manner, the criminal assailant is not made aware that police have been contacted.

Abstract: A ring detection device adapted to be connected in a telephone line to a telephone or telephone device. The device includes circuitry for distinguishing between several differently encoded telephone ring signals and enabling and/or maintaining disablement of the telephone or telephone device to which it is connected based upon such distinction. The device includes a switch for selecting which of the incoming telephone ring signals the telephone or telephone device to which is it connected is enabled.

Abstract: The telephone includes a touch sensor which may be attached on a handset. When the telephone receives a call meant therefor, the telephone alerts the user to the call by outputting a ringing tone through a speaker. In response to the call, the telephone also transmits a signaling tone to a base station which may be connected to the telephone over a radio channel and to a public switching telephone network. If the user touches the touch sensor in response to the ringing tone, the telephone stops the signaling tone and thus informs the base station that the user has responded to the call.

Abstract: A preferred duplex communications device includes a speaker for transmitting a signal received from a remote source, first and second microphones for transducing received acoustical signals wherein the first microphone is positioned significantly closer to the speaker than the second microphone so that the first microphone receives significantly more acoustical signal strength from the speaker than the second microphone. A first amplifier is connected to the first microphone and a second amplifier is connected to the second microphone wherein the second amplifier has a gain relative to a gain of the first amplifier such that the output signals of the first and second amplifiers are generally equal with respect to signals received by way of the speaker. A filter is then connected to the outputs of the first and second amplifiers to filter the signals transduced from the speaker thereby preventing transmission to the remote source of essentially all of the signals from the speaker.

Abstract: A telephone subset has a dial circuit (2) which can be powered from the exchange line (11, 12) via a regulated voltage terminal (VDD) of an associated transmission circuit (3) when the subset is OFF-HOOK and the line voltage is above a threshold voltage. When the subset is ON-HOOK, the dial circuit (2) is powered from a battery (B1) via a first switching circuit (TR2, TR3, R3). A hook-switch (HS) hold the first switching circuit OFF when the subset is OFF-HOOK to isolate the battery (B1) from line voltage. If the line voltage falls below the threshold when OFF-HOOK, a current sensing resistor (R4) switches a second switching circuit to connect the battery (B1) to the dial circuit (2) while the regulated voltage terminal presents a high impendance to isolate the battery from line voltage.

Abstract: A telephone line bridging sensor circuit is provided which provides a variable output frequency signal to a microprocessor for measuring and storing the frequency count on a periodic basis. The circuit includes an isolation transformer to isolate the audio component of the telephone line from the sensing circuit. The loop current present in the telephone line is rectified through a full wave diode rectifier and the output of the rectifier is filtered and regulated to provide an input voltage to an astable, voltage controlled oscillator. As the current on the telephone line varies, the input voltage to the oscillator also varies a proportionate amount causing the output frequency of the oscillator to change accordingly.

Abstract: A control device for a hands-free telephone set automatically controls microphone and amplifier gains so that a feedback loop has less than unity gain to avoid circuit instability and resultant self-oscillation. An emission channel includes a microphone, a signal compressor and a controllable attenuator. A reception channel includes a signal compressor, an adjustable attenuator and a loudspeaker. The combination of the emission and reception channels form an amplification loop whereby the output of the reception channel is acoustically coupled to the input of the emission channel while the output of the emission channel is coupled to the input of the reception channel through a common telephone line. To avoid circuit oscillation, a circuit initially sets the gain of the loop to a predetermined value slightly less than unity (0 db) and subsequently maintains the loop gain constant by maintaining the sum of the compressor and attenuator gains at a fixed value.

Abstract: A signal level expansion system for use in a telephone device is described which includes a level expansion circuit and an optional microphone enclosure. The circuit includes a voltage divider circuit which is used as a variable attenuator. The voltage divider has a junction field effect transistor (JFET) in its takeoff leg. The signal provided by the voltage divider is applied to an amplifier and then fed to a switch which detects voice signals. When a voice signal is detected having a level above a predetermined threshold, a timing circuit is energized. The timing circuit is connected to the JFET and, when energized, tends to increase the resistance in the takeoff leg of the voltage divider, increasing the signal level applied to the amplifier. The microphone enclosure surrounds the sides of the microphone with layers of rigid and resilient materials.

Abstract: The present invention is a channel changing system in a mobile unit communication system comprising a plurality of radio base stations for communicating with movable stations through radio channels and a center station for accommodating such base stations and connecting these base stations with the public telephone network. The center station is configurated comprising a private branch exchanger for accommodating the public telephone network and the lines extending from a plurality of base stations and a controller for controlling changing of communication channels by supervising the signal receiving levels between a movable station and a plurality of base stations. The controller is configurated so that it issues a channel changing command by detecting, based on the signal receiving levels, that a movable station has transferred to the radio zone of an adjacent base station from the radio zone of a certain base station.

Abstract: A cordless telephone system comprises a radio telephone set and a connection unit connected to a wire telephone circuit and also connected to the radio telephone set through a radio communication circuit, for interconnection control between the wire telephone circuit and the radio telephone set. When the wire telephone circuit is put in an unusable state or a signal on the radio communication circuit is put in an unreceivable state, the connection unit transmits a disconnecting signal to the wireless telephone set to forcibly cut off the radio communication circuit.

Abstract: Within a digital PBX system or the like, an appartaus permits provision of digital composite tone alerting particularly suitable for piezoelectric transducers with one arbitrarily selectable tone, by means of logic circuits for latching the sign-bit in a received PCM signal that exceeds a validity threshold, and by combining the toggling sign-bit with another tone to yield the composite tone.

Abstract: A unique dual-bandwidth cellular telephone includes a transceiver (100) having a dual bandwidth receiver, an audio/logic unit (200) having dual control programs, and a handset unit (300). The dual bandwidth receiver of the transceiver (100) has different filters (408 and 410) in the intermediate frequency section thereof which are switchably selected depending on which cellular telephone system is available. When service is not available in one of the cellular telephone systems, the unique cellular telephone automatically switches the receiver bandwidth and control program for operating on the other cellular telephone system.

Abstract: A fully functional writing pen having incorporated therein electronic circuitry including a miniature microphone and earpiece speaker serving as a handset in a cordless telephone system. The cordless pen handset microphone and earpiece communicate via an ultrasonic link to an ultrasonic transceiver provided in a portable, pocket-sized keypad telephone dialer, which provides a cordless RF link to a base station connected by conventional means to a telephone network. The keypad dialer also may communicate on a cellular phone network using a transvertor as an adaptor, alternatively direct person-to-person communication with DPRS handsets or other similarly equipped users is possible without the telephone network. A set of depressable control buttons on the pen body enable fingertip control of the cordless telephone system, including an on-hook/off-hook switch control button and mute control button for private conversation screening during telephone calls.

Abstract: A cellular telephone apparatus in which several functions such as decoding and encoding data signals, detecting the busy/idle bit and transponding the SAT signal, are carried out by a CMOS data processor (20) which is separate from a CMOS micro-controller (34). The data processor (20) can be operated at a lower clock frequency (1.2 MHz) than the micro-controller (34) which enables current to be saved compared to processing these functions in software using the micro-controller.

Abstract: A balanced transmission device having a pair of impedance element mutually of an equal value and connected between a pair of connecting terminals and an earthing point of an apparatus for superposing alternating signals on a direct current source and transmitting them through parallel two-wire cables. A transformer inserted as a high impedance source with respect to the apparatus for superposing and the transmitter, whereby the device can restrain any noise influence to realize smooth superposed transmission, with simpler arrangement but without enlarging it.

Abstract: A current switch that is responsive to logic switching control signals is used in a telephone circuit comprising a handset receive signal path and a speakerphone receive signal path for separation a received voice signal into either the handset or speakerphone receive path depending on the selected mode of operation of the telephone circuit. The current switch includes a pair of switched current mirrors and clamp circuits which are rendered active or inactive depending on the particular mode of operation. The clamp circuits maintain the dc voltage appearing at the input of each current mirror constant as the particular current mirror is switched between active and inactive states thereby inhibiting audible dc transients.

Abstract: Terminal apparatus is disclosed which alternatively connects a data terminal apparatus by a first switching unit to a line. The terminal apparatus includes a telephone, on-hook transmit circuit, and second switching unit for connecting the telephone set and on-hook transmit circuit alternatively to the line via the first switching unit. The on-hook transmit circuit includes a unit responsive to an on-hook transmit operation to switch the second switching unit to an on-hook transmit circuit, unit responsive to a dial signal transmit operation to transmit the dial signal to the line, direct current closing unit which continues to be connected to the line with the second switching unit switched to the on-hook transmit circuit, line release detection unit and control unit. The line release detection unit generates a line release detection signal when the line release detection unit detects the line as being released.

Abstract: A cordless telephone having a base unit with automatic telephone answering function and a portable unit has an engaging means for forming an engaging circuit upon an incoming call from a calling party, when the portable unit is kept in the off-hook state over a preset period of time during sending of outgoing message from the base unit, and an outgoing message inhibiting circuit which activated by output of preset timer means and inhibit outgoing message then both parties' conversation can be recorded in recording means on base unit which is set in stand-by mode.