Abstract: A ring generator circuit provides both a ring signal and talk battery to a subscriber telephone line. The ring generator recognizes whether talk battery voltage or a ring signal voltage is required and supplies the right voltage without the use of external relays. A switching network is coupled to the primary of a transformer to generate AC power at the transformer secondary. The switches intermittently conduct current from a DC power source through the primary of the transformer at a frequency substantially greater than the ring signal. A rectifier circuit converts the generated AC power into DC power to be provided to the telephone line. A sampling circuit samples the AC power, and the sampled power is additively combined with the DC power from the rectifier to form a ring signal component whose frequency is equal to the difference between the sampling frequency and the AC power frequency.

Abstract: An apparatus and method for facilitating interaction during a communication session between an analog modem and a terminal adapter for conveying digital alert tones and control data therebetween is provided. The embodiments provide for a collateral digital communication path between a microcontroller of an analog modem and a microcontroller of a terminal adapter for selectively relaying digital alert tones and control data therebetween. One embodiment utilizes a cellular interface of an analog modem for tapping and evaluating information for the presence of control data. Upon successful identification of control data, the microcontroller of a terminal adapter is notified and the specific control data detected in identified. By providing a method of apparatus for digitally relaying control data, accuracy of identification of control data by a terminal adapter is enhanced by foregoing needless signal transformation and retransformation.

Abstract: An off-hook/on-hook signal discriminating means 5a is provided in a control portion 5 of the FSU in order to make discrimination between a pulse dial signal and a hooking signal. When a telephone turns to an off-hook state after an on-hook state and turns to an on-hook state again and the on-hook state is continued for a predetermined time, the FSU performs a terminating process so as to be returned into a standby state. When an off-hook signal is detected again in a time smaller than a predetermined time, the FSU recognizes that the signal is either a dial pulse signal or a hooking signal, and the off-hook/on-hook signal discriminating means 5a monitors the time required for detecting an on-hook signal again. When the time required for detecting an on-hook signal again is smaller than the predetermined time, the FSU decides that the signal is a dial pulse signal, and controls a tone generating circuit 7f to stop the dial tone.

Abstract: A user-authentication system includes an authorized user device (AUD) for transmission of dtmf tones to a user-verification system (UVS) over a telephone network, where user-verification is performed and authorized users are granted access to a desired service. In a memory module of the AUD, a plurality of passphrases and identifying data are stored for subsequent transmission to the UVS. The compensating system comprises a pair of tone devices that generate low frequency tones and high frequency tones, respective that are amplified to different amplification levels. The amplification levels compensate for the low and high frequency tone transmission characteristics associated with different microphones in use in a public telephone system. The systems further performs channel normalization with the user-activated AUD and the UVS. Tone signals representative of the access telephone number transmitted by the AUD to reach the UVS, have a reference amplitude of zero.

Abstract: A fixed wireless access subscriber unit containing a wireless transceiver and a telephone subscriber line interface circuit which supports privacy and remote release of hold between the subscriber unit and extension telephones are disclosed. The subscriber unit detects when the primary handset, or an extension telephone set goes off-hook. In response the subscriber unit modifies the voltage and/or current characteristics on the telephone subscriber line which connects the extension sets to the subscriber unit in such a manner that extension sets connected to the telephone subscriber line will sense when the primary handset goes off-hook.

Abstract: In a communication terminal equipment and in a method of controlling call incoming, unnecessary noises in a period from the start of an alert sound to carrying out of the next operation can be reduced. When a predetermined operation is effected under the condition that an alert sound is ringing, the alert sound is stopped or the volume of the alert sound is reduced at least over a duration of call incoming. Thus, such a fear that persons in the surroundings may be troubled by the continuous ringing of the alert sound can be remarkably reduced. Further, since the situation that a power supply is cut off forcibly during call origination can be avoided, the fear that a person on the call origination side may be given an unpleasant feeling can be eliminated.

Abstract: In a circuit for notifying ring signal reception to a wireless telephone in a wireless/wired composite telephone system having a direct-current (DC) blocking circuit for blocking a DC component from a ring signal input through a ring terminal and a tip terminal and a ring detector for adjusting output signals depending on the ring signal having frequency components, a ring detecting circuit including an optical coupler for blocking a negative portion of an inputted signal received from the ring detector and for inverting a positive portion and for outputting a signal corresponding thereto, and a filter for receiving the signal output from the optical coupler and for generating a ring detection signal.

Abstract: A microphone system is provided for picking up ambient sounds including noises and for producing a sound voltage signal. A threshold is obtained from the sound voltage signal for determining a response voice spoken by an addressee in response to the bell tone. A response sound voltage based on the response voice is compared with the threshold, and a response voice signal is produced when the comparison is established. In response to the response voice signal, a line of the telephone is closed.

Abstract: A power converter forming part of a telephone subscriber line interface circuit selectively generates a ringing signal waveform, for supply to the line, or a supply voltage for a driver circuit for providing loop current on the line. First and second fixed frequency PWM signals are used to control the power converter, and hence the voltage which it generates, for the ringing signal waveform and the supply voltage respectively. The first PWM signal enables the power converter to provide a high power level needed for ringing signals. The second PWM signal has a lower frequency, and hence results in lower switching losses and power dissipation, and a lower duty cycle, suitable for the lower power level needed for the supply voltage, and is conveniently produced by masking pulses of the first PWM signal. The frequency of the second PWM signal is greater than 270 kHz, to avoid transmitting spectral energy to the line below this frequency.

Abstract: The present invention comprises a ringer interface circuit for generating a ringer signal for controlling a telephone ringer. The circuit of the present invention includes a first frequency divider, a second frequency divider, and a third frequency divider. The first frequency divider is adapted to receive a ringer clock signal and generate a first divider frequency output therefrom. The second frequency divider is coupled to receive the first divider frequency output and is adapted to generate a second divider frequency output using the first divider frequency output. The second frequency divider is further adapted to generate a oversampled audio frequency signal. The third frequency divider is coupled to receive the second frequency divider output and is adapted to generate a period signal using the second frequency divider output.

Abstract: A communication apparatus has a power saving stand-by mode for reducing power consumption during stand-by and a non-ringing call receiving mode for communication without ringing an attached telephone set at the arrival of a call. In the power saving stand-by mode, an operation state of a relay for attaining the non-ringing call receiving mode is held by a stand-by power supply to render both modes compatible to each other.

Abstract: A reduced complexity method of ring signal detection, in which a digital signal processor monitors an incoming data stream for zero crossings and employs a limiter-discriminator to differentiate ring frequency signals from line noise. Controlled noise is injected into the incoming data stream in order to prevent false declarations of ring signals in the presence of low frequency natural noise or low amplitude signals. The method conserves valuable processing power and may therefore prove useful in DSP-based telephone devices that must simultaneously perform multiple processing operations such as ring detection and speech processing.

Abstract: A system for alerting some individuals in a large open space such as a store or restaurant to an incoming telephone call, but that avoids disturbing other individuals by loud ringing. Individuals carry miniature alerting units that are clipped to their clothing and that can also serve as identification badges. An incoming telephone call is received by a telephone ringer control which transmits a signal by a wireless medium to an alerting unit, which emits a low-level auditory (or vibratory or visual) signal to alert the user, and also transmits an acknowledgment signal by the same wireless medium back to the telephone ringer control. If such an acknowledgment signal is not received within a short time period at the telephone ringer control, a loud auditory ringing signal is broadcast.

Abstract: An adjustable-period dual-tone multifrequency (DTMF) generator, which includes a plurality of programmable counters or up/down counters, a control unit, a memory unit for storing data, a digital adder, and a digital-to-analog converter. The programmable counter and the control unit are combined together to form into at least two programmable counting address generators, in which the circuit is a digit-process circuit for overcoming the problem of signal distortion that usually exists in an analog circuit.

Abstract: A technique for powering telephone lines using an unbalanced current source and current sink; and a technique for improving attenuation/frequency distribution and return loss (impedance matching) of transformer-coupled wire-line communications circuits by using secondary series capacitance and an AC current pump signal source; and a generation of ringing voltage as positive voltage pulses with respect to a negative power supply voltage; and a technique for removal of AC power ripple by using an active linear floating filter for the purpose of powering telephone line circuits, and a technique for injection of real time tone samples into T1 transmissions circuits by use of a T1 framer idle code register.

Abstract: Acoustic dialers are widely used to dial telephone numbers by generating a pair of DTMF tones for each key being depressed. Non-linearities in telephone systems, acoustic dialer loudspeakers, and telephone microphones may cause interfering tones to be produced due to mixing of generated DTMF tones. These interfering tones are especially problematic when they are near the frequencies of the DTMF tones and have similar amplitudes. When these interfering tones are received by a receiver decoder, the decoder may be unable to distinguish the interfering tones from the DTMF tones, and consequently the decoder may reject the DTMF tones received. The present invention prevents these types of rejections by generating a supplemental tone in addition to the normal DTMF tones. This supplemental tone attenuates the interfering tones so that receiver decoders can distinguish the interfering tones from the DTMF tones.

Abstract: A telephone has a receiver, a transmitter, a control interface, an audio processor and a microprocessor. The audio processor includes a digital signal processor, an input audio unit coupled to a microphone, an output audio unit coupled to a speaker, and a ring signal controller coupled to a transducer/ringer. When an incoming call is received, the audio processor samples the microphone input signal, which is indicative of ambient noise, and performs a spectral analysis of the ambient noise. The audio processor then sets the ring frequency and the ring volume responsive to the ambient noise spectrum and the ring volume control level set by the user.

Abstract: A telephone ringing signal generator includes a DC converter for producing high positive and negative voltages that define peak amplitudes of the ringing signal, which is produced by low pass filtering a generally trapezoidal waveform having these peak amplitudes. The generally trapezoidal waveform is produced by a level-shifting integrator at a frequency determined by a low voltage square wave supplied to the integrator. The integrator comprises a capacitor coupled between a virtual ground point and an output of the integrator and arranged to be charged with two opposite polarities in response to opposite transitions of the square wave, and a resistor via which the square wave is supplied to the virtual ground point. Buffers are provided for buffering the trapezoidal waveform supplied to, and the ringing signal produced by, the low pass filter.

Abstract: A telephone call alerting system is applied to a telephone communication system accommodating a line to which a telephone terminal is connected, a plurality of telephone numbers being assigned to the line.

Abstract: An acoustic feedback suppression system, particularly for auxiliary ringers in socket telephone systems, comprising a first terminal and a second terminal of a telephone line, an internal ringer, and an auxiliary ringer that is connected between the first and second telephone lines. The system comprises an activation circuit adapted to activate first and second switching circuits to reduce the voltage at the terminals of the auxiliary ringer, the activation circuit being controlled by an activation signal generated by a control and signaling circuit when a user dials a telephone number.

Abstract: The total energy of a signal that has entered from a telephone line is detected before the signal is applied to an AGC circuit. After the signal is applied to the AGC circuit, the energy of a DTMF signal, which comprises one frequency from four high group frequencies and one frequency from four low group frequencies, is detected through a band-elimination filter having a short energy-propagation delay time with respect to pass-band frequencies. By detecting the DTMF signal based upon the detected energies, detection of the DTMF signal can be performed in a short period of time and erroneous detection can be suppressed.

Abstract: A telephone interface circuit with impedance termination during call pauses, comprising first and second terminals to connect to a telephone line and a line termination branch connected to the first terminal across a decoupling capacitor, and to the second terminal. The line termination branch includes an intersection node, a first switch and a first impedance resistor between the first terminal and the intersection node, and a second switch and a second impedance resistor between the second terminal and the intersection node. The intersection node is connected to ground across a third switch. The first switch, the second switch, and the third switch are controlled by a control unit by first, second and third control lines, respectively. The telephone interface circuit further comprises a ring signal detector that is connected to a microprocessor unit capable of activating the control unit in an interval in which the circuit must be terminated for CLID (Calling Line IDentification) transmission.

Abstract: A space and power efficient digitally controlled, all solid state, DC to AC converter powered by low voltage DC, typically found in logic circuits, that generate a high voltage low frequency AC output with a low slew rate waveform, suitable for activation of an electro-mechanical bell or electronic ringer in a telephone. The present invention is particularly suited for application in small, wireless terminals used to provide telephone services via satellite or terrestrial radio to single users or a small number of users as found in a PBX. The present invention is also particularly suited for battery or solar powered equipment where power efficiency is of significant value.

Abstract: A communication device, such as a telephone or a facsimile device, includes an input device for inputting code information for a call to be transmitted through a communication network, a transmitting device for transmitting dual-tone multiple frequency (DTMF) signals to the communication network according to the code information, and a transmission control device for controlling transmission parameters of a DTMF signal. At least one of a plurality of parameters, including signal transmission time, signal pause time, and signal transmission level, is made different by the transmission control device for a DTMF signal transmitted during the call by the transmitting device after the execution of a dialing input from the communication device to the communication network.

Abstract: A technique for powering telephone lines using an unbalance current source and current sink; and a technique for improving attenuation/frequency distribution and return loss (impedance matching) of transformer-coupled wire-line communications circuits by using secondary series capacitance and an AC current pump signal source; and a generation of ringing voltage as positive voltage pulses with respect to a negative power supply voltage; and a technique for removal of AC power ripple by using an active linear floating filter for the purpose of powering telephone line circuits, and a technique for injection of real time tone samples into T1 transmissions circuits by use of a T1 framer idle code register.

Abstract: A programmable timer circuit having ON and OFF volume control states; for controlling the volume of audible signals generated by a signal generator of a communication device at preprogrammed times is disclosed. The programmable timer circuit monitors a communication link for the presence of signals indicative of an incoming communication. When such signals are detected and the volume control state of the timer circuit is ON, the volume of the audible signals generated by the signal generator of the communication device is adjusted so that such audible signals are broadcast with a programmed loudness. Volume control of the audible signals generated by the signal generator does not prevent outgoing communications using the communication device. The fact that the volume of the audible signals generated by the signal generator is controlled, is not apparent to the calling party.

Abstract: In a portable telephone set comprising a receiver for generating an audible tone, a vibrator for vibrating the portable telephone set mechanically, and a radio section for receiving an incoming call signal to produce a call detection signal, a transmitter microphone senses, in cooperation with a voice processing section, ambient sounds to produce an ambient sound level signal. In cooperation with a main control section, a vibrator control section selectively activates, in response to the call detection signal, one of the receiver and the vibrator with reference to the ambient sound level signal. When the level is not more than a predetermined level, the vibrator control section drive the vibrator to make the vibrator vibrate mechanically without generation of the audible tone. Otherwise, the vibrator control section makes the receiver generate the audible tone.

Abstract: An off-hook telephone clearing system for a telephone line having at least two telephones connected thereto, comprising a howler tone detector connected to each telephone, and a telephone disconnect device having an input responsive to the howler tone detector for disconnecting a telephone being in off-hook condition from the telephone line. The clearing system may include a latching relay in the disconnect device. The latching relay may be mechanically coupled to the telephone hookswitch for delatching upon hang-up of the receiver.

Abstract: A novel telephone system and method for activating a speakerphone in response to an incoming call based upon the presence or absence of a subscriber within a predetermined proximity zone. The telephone system has a ring detector for detecting a ring signal in response to an incoming call received via a central switching network, a proximity sensor for sensing the presence or absence of a subscriber within a predetermined proximity zone of the telephone system, and a control unit for automatically activating the speakerphone to establish communication with the caller when the subscriber is within the predetermined proximity zone and deactivating the speakerphone in response to detecting a busy tone generated by the central switching network when the call is terminated.

Abstract: A method of and apparatus for providing compatible universal identification telephone protocols by generating predetermined unique audio sequences recognizable by the telephone user as defining standardized Audio Icon information and distinct from and separated from one another and other telephonically transmitted signals; sending and receiving such generated audio sequences on a public switched telephone network having paths the parameters of which fall within predetermined specified training sets, including modem performance standards; and assuring recognition and correct identification of such audio sequences conveyed along such paths.

Abstract: A telephone set using two or more telephone numbers called by respective call signals having different patterns, which are stored in a pattern data memory when the call signals are received and detected in a registering mode and with which the pattern of a call signal received when the telephone set is not in the registering mode is compared to determine the telephone number being called. The registering mode is established by an operator-controlled data input device. The patterns of the call signals are detected by a pattern detector in the registering mode, and the detected patterns are registered in the pattern data memory, so that the telephone number called by each call signal is determined by a pattern determining device as a result of comparison of the pattern of each call signal with the registered patterns in the pattern data memory. The telephone set preferably has an indicator for indicating on and off patterns of the call signals stored in a temporary memory.

Abstract: A telephone line interface circuit comprises a controlled voltage generator for selectively generating a ringing voltage waveform for a telephone line or a supply voltage for a drive circuit for the telephone line, and a switching circuit interconnecting an output of the controlled voltage generator, the drive circuit, and the telephone line accordingly. In order to avoid creating a potentially hazardous condition on the telephone line, an interlock is provided between enabling of the controlled voltage generator and switching of the switching circuit, and software and hardware monitoring functions monitor operation of the control software and the controlled voltage generator and disable the controlled voltage generator in response to fault conditions or unusual behavior.

Abstract: A line-feed circuit which is controllable by logic level control signals from a local microprocessor. One of the logic level signals is a 20 Hz clock signal with a duty cycle of 20 ms high and 30 ms low. Another is an enable signal that allows the ringing driver either to be turned on (and which places the line-feed circuit into a disconnect or "open interval" state so as not to load the ringing signal) or off in which case the ringing driver is placed into a high impedance state so that it will not load signals appearing on the Ring conductor. This permits the ringing driver to be connected directly to the Ring conductor without the need for a series isolating element such as an electromechanical relay or comparable solid state device. The nature of the ringing driver allows the use of a simple ring trip detector comprised of a voltage comparator and duty cycle detector.

Abstract: A wireless terminal utilizing digital radio processing utilizes stored program control to allow the wireless terminal to operate in a plurality of disposed wireless communication systems. In particular, the digital radio processing with appropriate stored program control operates in a plurality of wireless communication system by selectively and controllably enabling selection of frequency, channel bandwidth, modulation type, channel coding and source coding operational components appropriate to the communication system that the wireless unit is to operate in. A function control enables the wireless terminal to actively seek out and search for availability of wireless communications system in which it may operate.

Abstract: A key telephone system (KTS) or a telephone private branch exchange (PBX) card is integrated into a personal computer to provide telephone system features. The telephone card includes a call controller, a switching network and an interface bus controller for coupling data signals between the PCI bus and an internal bus of the call controller whereby the telephone card is able to communicate with resources of the PC such as a LAN and a hard disk bulk memory for executing telecommunications functions. In this arrangement the PCI bus must carry both asynchronous data processing and control signals as well as reformatted synchronous signals. The addition of a synchronous bus for transporting synchronous signals is used to couple these signals between the switching network, a telephony features controller and the hard disk bulk memory. The use of the synchronous bus provides for improved telephone traffic capacity and PC functionality.

Abstract: A power-cross detection circuit includes a zero crossing detection circuit for detecting a first zero crossing of the current from a first positive half-cycle to a first negative half-cycle, a second zero crossing of the current from a second positive half-cycle to a second negative half-cycle, and a third zero crossing of the current from a third positive half-cycle to a third negative half-cycle and a circuit for detecting a voltage level and outputting a first signal when the voltage level exceeds a predetermined voltage level, between the first zero crossing and the second zero crossing and between the second zero crossing and the third zero crossing. The zero crossing detection circuit outputs a second signal based on the first, second and third zero crossings.

Abstract: An impulse convertor for converting a received telephone impulse dialing signal into a restored dialing signal has a limiter-amplifier, a signal detector, an output formatter, and a controller. The limiter-amplifier receives the impulse dialing signal from an interface b to a communication system such as a public switched telephone network or a cellular network, limits the amplitude range of the received impulse dialing signal, and compensates for attenuation of the received impulse dialing signal. The signal detector analyzes successive portions of an output signal generated by the limiter-amplifier and determines dialed digits represented by the received impulse dialing signal. The output formatter converts the dialed digits determined by the signal detector into the restored dialing signal that is provided to a device C such as a PABX. The controller coordinates operation of the limiter-amplifier, signal detector, and output formatter.

Abstract: A system and method for modifying a composite Ring AC/Message Waiting (RAC/MW) signal to prevent bell tap on analog telephones. The composite RAC/MW signal comprises AC signals and DC signal alternately spaced in time. At a zero crossover point the composite RAC/MW signal is ramped from a given bias voltage level to a desired Message Waiting voltage level at a slope sufficient to prevent bell tap. Near the end of the Message Waiting portion of the composite signal the composite signal is ramped to the bias voltage level at a slope sufficient to prevent bell tap.

Abstract: A ring generator circuit that produces a ring output for a plurality of telephones simultaneously. The ring generator circuit includes a switch that receives an oscillating signal in response to an on condition of an on/off signal. The on/off signal is related to whether an incoming phone call is directed to one of the plurality of telephones or not. The ring generator circuit also includes a DC offset circuit that receives a DC input potential, an amplifier stage for providing a ring output, and a feedback circuit connected between the ring output of the amplifier stage and the switch output.

Abstract: An inadvertent-off-hook-condition detecting apparatus for use with a telephone connected to a telephone system is described. The telephone has a hookswitch which connects the voice network of the telephone system across the input lines to the telephone when the hookswitch is in an off-hook position, and which disconnects the voice network from the telephone input lines when the hookswitch is in an on-hook position.

Abstract: An auto-dialer suitable for use as a smart card capable of being acoustically coupled to a telephone and being reprogrammed in response to acoustic signals. The programming and other features of the auto-dialer can be enabled or disabled by the auto-dialer in response to persecuted signals, e.g., a string of DTMF tones. Encryption of calling card and other data into destination telephone numbers is achieved by selectively altering persecuted characteristics of a DTMF tone sequence, such as the duration of tones, the period of silence between tones and the twist between Lo-band and Hi-band tones of DTMF tone pairs in a DTMF tone sequence representing a telephone number. The encryption of data into the telephone number does not affect the ability of standard telephone switching circuitry to recognize the destination number.

Abstract: An ISDN interface unit interconnects a data processing unit, an ISDN, and an analog telephone and includes a ring sound controller for supplying a control signal to designate a generation of a ring of the analog telephone through a modular jack; a ring signal generator generating a ring sound; a switch selecting one of the ring sounds generated and supplying the ring sound to the analog telephone. Further, the ISDN interface unit comprises communication functions for the digital signal and for the voice band signal, a control channel signal sent from the ISDN line is interpreted, and one of the communication functions can be selected.

Abstract: In a digital data communications device for use in an ISDN environment, a power supply apparatus and method are provided for energizing telephone danger circuitry or other alerting mechanisms. Embodiments of the present invention employ signal generators which control switching circuitry that converts a low voltage DC power source into a low voltage alternating current. A step-up transformer is used to convert or transform this low voltage into a high voltage alternating current, which is rectified and filtered to generate a high voltage direct current. The signal generators also control the switching circuitry which applies this high voltage direct current to an alerting mechanism and alternately provides a path to discharge energy which may be stored in the alerting mechanism, causing the alerting mechanism or other ringer circuitry to resound.

Abstract: A circuitry is disclosed for superimposing small, low energy (2) and large substantially higher energy (3) signals, in particular for transmitting speech signals with a remote supply direct signal for a receiving circuit or with a high energy alternating signal, for example a call alternating voltage for signaling. The circuitry includes an operational amplifier (1), having one input connected to a pole of a source supplying the small signal and operational voltage inputs being connected to a voltage supply source. In order to allow low energy, weak signals, such as speech signals, and high energy signals and direct voltages to be transmitted by such a circuitry over a subscriber line by means of simple components, the second pole of the small signal source (2) is connected to the second input of the operational amplifier (1) and one pole of a higher energy signal supply source (3) is connected to one pole of the voltage supply source (V).

Abstract: In a telephone exchange apparatus for performing exchange processing by a memory time switch, first tone signals are generated, and second tone signals are generated by sequentially exchange-controlling the memory time switch in synchronism with the zero-crossing points of the generated first tone signals. Furthermore, when the second tone signals are sent to corresponding output time slots, the switching operation is performed in synchronism with the zero-crossing points of the second tone signals, so that high-quality tones including no harmonic component can be sent to an extension telephone set or to another system through an outside line.

Abstract: A ringer circuit comprising a rectifier circuit, a voltage regulator and a ringer generation circuit is provided. The rectifier circuit generates a DC voltage signal at an output terminal and has an input terminal adapted to receive a ring input signal and a ground terminal. The voltage regulator generates a voltage signal, responsive to the DC voltage signal. The ringer generation circuit outputs a ring audio, responsive to the voltage signal. As a voltage level of the ring input signal exceeds a predetermined value, the voltage signal substantially equals to a fixed value, and as the voltage level of the ring input signal does not exceed the predetermined value, the voltage signal substantially equals to the DC voltage signal.

Abstract: An electronic ring monitoring device is disclosed that includes telecommunications interface circuitry, ring detection circuitry, isolation circuitry, and output driver circuitry. The telecommunications interface circuitry may include a switch allowing programmable selection of alternate connections to the telecommunications source depending upon the particular source involved. The ring detection circuitry may include a bridge rectifier, a filtering capacitor, a bleeder resistor to prevent false detection from stray voltages on the telecommunications line, and a variable resistor to allow a programmable detection level. The isolation circuitry may include a optical isolator that will electronically isolate the telecommunications side of the device from the output side of the device. The driver circuitry may include a triac that allows current flow when a ring is indicated and may include inductive load protection circuitry.

Abstract: A cordless telephone that may be fully powered by AC main power lines and only partially powered by telephone lines includes structure for producing dual tones, structure for producing dual-tone multifrequency tones from the dual tones, and structure for empowering each of the foregoing in the event of AC main power failure where the only power available passes through the telephone lines.

Abstract: A telephone switching system is comprised of a main controller, switching circuits controlled by the main controller, a peripheral controller for controlling the seizing of subscriber lines for calls routed through the switching circuits, and further comprising a first memory associated with and accessible by the main controller for storing user data associated with each directory number, the user data comprising a ring type, a second memory associated with the peripheral controller for storing ringing cadence indicators associated with respective plural ring types, the main controller for reading the station data from the first memory upon receiving a request for service to a directory number, and sending the ring type indicator with a subscriber line seize message to the peripheral controller, the peripheral controller for reading the second memory and obtaining the ring cadence indicators associated with the ring type, and ringing a line according to the indicated ring cadence.

Abstract: A ringing generator and a method for converting a DC input voltage signal from a DC source to an AC output voltage and supplying this output voltage to a variable load, The output signal has a continuously adjustable amplitude so as to continuously adapt to the current demanded by the load, A power supply converts the DC input voltage to variable DC supply voltages. A linear amplifier then converts these variable supply voltages to an AC output voltage using a precision sine wave oscillator as a reference. A load current sensor senses and measures the output current being supplied to the load and then a control circuit is employed to automatically and continuously adjust the amplitude of the output voltage to maintain the maximum output current that can be safely supplied to the load by the linear amplifier.