Abstract: A communication peripheral apparatus automatic line searcher includes a CPU (central processing unit) connected to two ring detectors, two hold detectors, two in-use detectors and a loop detector, the ring detectors, hold detectors and in-use detectors being respectively connected to a first telephone line and a second telephone line, the first telephone line and the second telephone line being respectively connected to contacts of a first relay, the first relay having a center contact connected to the normal-close contact of a second relay. The CPU automatically switches the vacant telephone to the vacant telephone line upon a call through one telephone line. The relays are switched to drive the phone power through the CPU to indicate the in-use status of the corresponding telephone line.

Abstract: A facsimile machine (1) comprises an off-hook device (14) for ascertaining whether a telephone set (2) connected to a telephone line (TL) in parallel with the facsimile machine (1) has already taken an incoming call, which call is featured by a ringing signal in the telephone signal (TS). For this purpose, the off-hook device (14) compares the voltage value of the DC component (G(TS)) of the telephone signal (TS) with off-hook thresholds (OSW1, OSW2) and, if necessary, produces off-hook detection information (ODI1, ODI2) or fax off-hook information (FAI). Since the voltage values of the DC component (G(TS)) of the telephone signal (TS)—more particularly in a private branch exchange—may be lower than specified, in response to which the off-hook device (14) could determine a false outcome, the off-hook device (14) activates an error mode when the off-hook detection information (ODI1) is produced simultaneously with the ringing signal detection.

Abstract: The present invention relates to an arrangement, for improving a telephone system in which a plurality of analogue phones are connected to a single line, and for the purpose of providing an arrangement which can solve the problem related to interruption of an in progress conversation or modem connection in a group of parallelly connected telephones, it is according to the present invention suggested that said arrangement comprises voltage sensing means, said voltage sensing means being adapted to sense a first higher dc voltage across the line in standby mode, as well as a second lower dc voltage in the active (conversation) mode.

Abstract: A circuit for determining connection status of a phone line shared by multiple telecommunications devices, such as modems and phones, is provided. The phone line includes respective tip and ring lines. The circuit comprises a first transistor stage coupled to receive a signal indicative of a voltage difference between the respective tip and ring lines. The first transistor stage is configured to supply an output signal having a predetermined time response. The circuit further comprises a second transistor stage coupled to the first transistor stage and configured to supply an output signal having a slow time response relative to the output signal from the first transistor stage.

Abstract: A method for producing a hook-flash event on a loop (6B) incorporating a supervisory signal circuit. The supervisory signal circuit includes a supervisory signal source (2) that causes a supervisory current to flow around the loop through a threshhold detector device (4) and one or more supervised devices (10 and 24). When a counter-signal source (34) is connected to the loop, it opposes the flow of loop supervisory loop current (12), causing its level to drop below the detection threshhold of the threshhold detector device. After a timed period, the counter-signal source is disconnected from the loop, allowing the level of supervisory loop current to return to its normal state, thereby completing the hook-flash event on the loop.

Abstract: A filter according to an embodiment of the invention actively adapts terminal equipment and a subscriber line to each other by conforming to the electric properties of the subscriber line. Then the filter virtually changes the electric properties of the subscriber line more advantageous for the terminal equipment.

Abstract: The invention provides an apparatus for use with a subscriber line interface circuit in a telephone system, the subscriber line interface circuit being interposed between a telephone central office and a subscriber line, the subscriber line being coupled with a subscriber telephone device.

Abstract: An interface circuit including a galvanic isolation barrier between a transmission line and a user equipment, and a detector for detecting, independently from a transmission, the idle or busy state of the line.

Abstract: An apparatus for detecting a dual tone alert signal in a telephone system capable of at least off hook mode operation includes a processing channel for each tone. Each channel consists of a bandsplit filter for extracting the tone of interest and attenuating the other tone; a comparator for comparing the output of said bandsplit filter with a threshold value; and an adaptive threshold generator for generating said threshold value adapted to the amplitude of the output of said bandsplit filter to reject speech and music imitations. The apparatus offers improved talkdown and talkoff immunity.

Abstract: Apparatus and method for generating user warning signal during data transmission suspension or degradation, that allows an user to identify that parallel operation of plain old telephone system (POTS) and digital data communications equipment is either occurring or being attempted. More particularly, the user signal warning indicates the impact to the operation of a multiple channel data communications device as a result of the parallel operation with the POTS equipment. A multiple variable signal alerts the user to the parallel operation, the amount of degradation, the elapsed time of the degradation to data communications, and which user site is causing the degradation by the direction of the data traffic being impacted.

Abstract: A line circuit utilizing a differential amplifier whose output is regulated to zero volts D.C. (when the subscriber's set is off-hook) by a negative feedback circuit, for controlling a voltage controlled power supply which provides a constant current feed to the subscriber's loop. The differential amplifier also transmits audio signals received from the subscriber's loop directly to a PABX via an unbalanced terminal. When the loop range exceeds a predetermined threshold, the circuit reverts to a voltage feed operation thereby allowing operation over long loop lengths and the ability to provide on-hook CLASS services.

Abstract: The invention relates to a modem intended to be connected to a telephone line comprising a device for detecting the busy state, or the acquisition, of a telephone line. The detector includes a means sensitive to the energy supplied by the modem on its input/output (34) which is connected to the telephone line (38). The detector, which supplies a signal preventing the line being acquired if the line is already busy with another appliance, needs no electrical separation between the line and the modem.

Abstract: A system and method of limiting power consumption in a telecommunications equipment coupled between a plurality of far end subscriber lines and a plurality of near end subscriber lines are provided. The method includes monitoring and determining a number of ringing subscriber lines, comparing the number of ringing subscriber lines to a predetermined ringing threshold, monitoring and determining a number of off-hook subscriber lines, comparing the number of off-hook subscriber lines to a predetermined off-hook threshold, and blocking further ringing and/or off-hook subscriber lines in response to the number of ringing and/or off-hook subscriber lines reaching or exceeding the respective predetermined ringing and off-hook thresholds.

Abstract: The present invention relates to a telecommunication device and method which converts pulses generated by rotary dial phones to DTMF signals, allowing the use of CTI applications regardless of the type of telephone set used by the caller or the type of the CO switch. Pulses are identified by the device's algorithm and converted into appropriate DTMF signals. This device connects across in parallel with all the telephone lines on the subscriber side at the CO that require monitoring to detect loop current. Pulse dialing as well as overdialing from a rotary phone is thereby detected and these pulses are converted into DTMF signals, suitable for extended services. The device can also determine time and date of the call, number dialed by the user and also the length of the call from the end of the initial dialing to the disconnection of the line.

Abstract: A system and method for determining telephone status over a network. The system and method provides for off hook status to be determined by a switch or other monitor that then provides that information to a telephone status file. The telephone status file is accessible over the Internet by computer so that a calling party can first determine if the called party is on the telephone. Thus wasted time in making calls that cannot be completed is avoided. The system operates over normal PSTN's, over cable systems, and over the Internet.

Abstract: Monitor circuitry is disclosed that produces a loop current monitor signal indicative of the DC loop current passing through DC holding circuitry, which may be part of phone line side circuitry that may be connected to phone lines. This loop current monitor signal may be digitized and then communicated across an isolation barrier to powered side circuitry as digital information representative of the DC loop current levels in the phone lines. Example embodiments for the monitor circuitry are also disclosed, such as a MOS transistor, for which the monitor signal is the drain current of the MOS transistor, and an external resistor, for which the monitor signal is a voltage associated with the external resistor.

Abstract: A line card integrates subscriber line interface circuitry, A/D and D/A converters, and digital signal processing technology. The digital signal processing technology performs many line card tasks such as switch hook detection, ground key detection, DC feed control, polarity reversal, ringing tests, fault detection, power cross detection, and ring trip detection. A line card having a digital signal processor supports both integral and external ringing signal generators. During application of a ringing signal, the line card detects ring trip conditions while discriminating against short duration short circuits. The line card includes programmable features that facilitate adaptation to varying regional ring trip detection and short duration short circuit discrimination specifications and subscriber loop characteristics.

Abstract: An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and/or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points.

Abstract: Disclosed is a telephone alert system that comprises a telephone and a device for indicating that the telephone requires attending. The indicating device includes a call holding alert mechanism for alerting a party on hold that the hold initiating party is ready to resume conversation, and a further mechanism for alerting someone that the telephone handset is inadvertently disengaged from the switchhook. Both alert mechanisms make use of the alert tone of the telephone chassis ringer for notification purposes.

Abstract: A communication system is provided with a capacitive isolation barrier in which at least a portion of the ring detection circuits may be integrated into the line side circuitry. Moreover the ring detection circuits on the phone line side of the isolation barrier may be powered at least in part by power transmitted from the powered side of the isolation barrier to the phone line side of the isolation barrier through the barrier capacitors. A capacitive interface may directly connect the ringer circuitry on the phone line side of the barrier to the TIP/RING lines. The capacitive interface operates to linearly attenuate the TIP/RING signal voltage levels from the high phone line levels to levels within integrated circuit technology limitations.

Abstract: A ring trip circuit is incorporated in a telephone exchanger together with a call signal source and a relay unit connected between the call signal source and user's terminal, and determines current status of the user's terminal at a certain timing close to the zero level of a call signal changed across the zero level without influence of fluctuation of the call signal source, a loop resistance and a leak resistance, thereby preventing the user's terminal from undesirable interruption of the call signal.

Abstract: An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and/or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points.

Abstract: A line card integrates subscriber line interface circuitry, A/D and D/A converters, and digital signal processing technology. The digital signal processing technology performs many line card tasks such as switch hook detection, ground key detection, DC feed control, polarity reversal, ringing tests, fault detection, power cross detection, and ring trip detection. Actual subscriber loop parametric conditions may be determined by a digital signal processor using sensed small signals on both the A and B conductors of subscriber loop. By sensing small signals, saturation of sensing circuitry may be avoided. Furthermore, relatively high speed digital signal processing facilitates accurate and expeditious switch hook status determination.

Abstract: A telephone line state detecting device that is connectedly provided with a hardware detecting circuit when a telephone line is connected to a modem. The hardware detecting circuit is connected to a processing unit such that, in use, the hardware detecting circuit can detect pulses generated by voltages flowing through the telephone line. The pulses are being processed by the processing unit to judge whether the telephone is disconnected or the electrical contact thereof is deficient, or whether the telecommunications equipment used in conjunction therewith is busy or not in use.

Abstract: In a local loop telephone system, a voltage limited device having circuitry to provide subscriber interface functions and generate a ring signal. The device comprises four switches in a full bridge drive configuration. An external source provides a constant voltage which converted into an alternating ring voltage by triggering the switches in a specified sequence.

Abstract: A telephone ring signal detector distinguishes a telephone ring signal voltage from a telephone pre-ring signal voltage on a telecommunication line at a premise, and is unresponsive to the pre-ring voltage and responsive only to the ring signal voltage for providing a telephone ring signal detect output signal during a first quarter cycle time period of a first telephone ring signal. A line switch couples an off-hook terminal impedance to the line in response to the ring detect signal for the purpose to exchanging telecommunication signals to and from the line. The detector provides a signal translating device for translating the ring and pre-ring signal voltages into a translated telephone signal having a translated peak ring signal voltage and a translated peak pre-ring signal voltage.

Abstract: The communication system disclosed herein allows for the hookswitch devices to draw loop current from the phone line in both on-hook and off-hook conditions. Thus, even though an on-hook condition occurs, current may be obtained through the hookswitch devices. This feature allows circuitry which operates during on-hook conditions to still receive power from the phone line. Moreover because the hookswitch devices are utilized for drawing power in both on-hook and off-hook conditions, the use of additional switches dedicated to drawing the power during on-hook conditions is not required. For example, loop current may be drawn from the phone line through the hookswitch devices to power circuits used to perform the on-hook caller ID function. The powered circuits may include for example analog to digital converters. The technique disclosed herein for drawing current through the hookswitch devices is particularly useful for communications systems which utilize a capacitive isolation barrier system.

Abstract: An analog telephone subscriber terminal apparatus with means for realizing additional functions is provided. In the on-hook state of the subscriber terminal apparatus, and outside of the idle operating state of the subscriber terminal apparatus, a current supply device that draws current from the subscriber line and is integrated into the terminal apparatus is switched effective for the duration of the reception of data containing the additional functions. The current supply device provides the supply current to the means for realizing the additional functions, but is limited to such an extent that the increased subscriber line loop current that then flows is not indicated as a loop closure.

Abstract: A data access arrangement (DAA) for interfacing a modem with a telephone line which requires only one safety barrier device for providing electrical isolation of the modem from the telephone line for both a ring detection signal and a remote device hang-up detection signal transmitted from the DAA to the modem. The DAA utilizes the same combined circuitry to transmit both the ring detection signal and the hang-up detection signal to the modem. The single safety barrier device is selectively connected to either ring detection circuitry during an On-Hook mode or remote hang-up detection circuitry during an Off-Hook mode by a selectively operating a relay switching device. With this arrangement, an improved DAA is provided having a combined circuit configuration for communicating ring detection information to the modem during the On-Hook phase and communicating remote hang-up detection information to the modem during an Off Hook phase, thus minimizing the size, cost, and complexity of the DAA.

Abstract: In a subscriber line interface circuit, a device applies to a line, associated with the line interface circuit, a substantially constant line current of a first predetermined value for line voltages up to a first voltage having an absolute value which, by a predetermined amount, is lower than the supply voltage of the line interface circuit. For line voltages between the first voltage and a second voltage having an absolute value which, by a predetermined amount, is higher than the first voltage, a line current which is inversely proportional to the line voltage and of a value between said first predetermined value and a second predetermined, lower value is applied to the line. For line voltages between the second voltage and a third voltage having an absolute value which, by a predetermined amount, is higher than the second voltage, a substantially constant line current of the second predetermined value is applied to the line.

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: A telephone switching system 10 comprises a plurality of physical ports 20, and switches removable terminals based on predetermined connection information, wherein such connection information is arranged to be capable of being stored and rewritten in a RAM 60 by inputting from the terminal. When a physical port connecting to a terminal interface 30 is reconnected from a first terminal to a second terminal, a CPU 40 rewrites the connection information stored in the RAM 60 so that an extension number the user desires is stored for the physical port reconnected with the terminal.

Abstract: A digital telephone (60) comprises send equipment (40) and receive equipment (50), coupled via a signal splitter/combiner (61) onto a digital telephone line (62) for communication with a remote party (90). The send equipment (40) comprises an A-law map (12) and a mu-law map (43). Receive equipment (50) comprises an inverse A-law map (14) and an inverse mu-law map (52). Maps (12,43) are selectable by the user (80). Similarly, inverse maps (14,52) are also selectable by the user (80). Receive equipment (50) may further comprise an un-quick-fix module (55) for removing unwanted insertions of quick fixes (25) inserted into the telephone line (62) by international telephone companies. Receive equipment (50) may further comprise a digital signal processor (57), computer (56), a set of pre-stored templates (58) corresponding to possible incoming telephone characteristics, and a caller parameter decipher module (51).

Abstract: A ring trip detector has a voltage difference detector with first and second inputs, for supplying an off-hook signal upon detection of a voltage difference. The ring trip detector also has a switch extending between the first and second inputs of the voltage difference detector. The ring trip detector detects when a telephone current starts to flow through a sensing resistor having first and second ends and to a telephone set. The switch closes upon an initial current flow through the sensing resistor and then opens. The ring trip detector has a pulse generating mechanism having two inputs respectively connected to the first and second ends of the sensing resistor. The pulse generating mechanism has an output and generates a pulse at the output when current starts to flow through the sensing resistor. The switch has a trigger connected to the output of the pulse generating mechanism for closing the switch when the pulse is generated. A differentiator mechanism may be used as the pulse generating mechanism.

Abstract: The present invention provides a voice monitoring system for remote subscribers, which enables voice monitoring for even those calls which are set in speech mode after connected by drop-back in remote local equipment without the intervention of a time division switch in a telephone network. The voice monitoring system for remote subscribers offered by this invention is intended for voice monitoring for subscribers accommodated by remote local equipment connected to a time division switch in a telephone network.

Abstract: A signal detector 100 and method detects digital signals on a signal path 102. The signal detector 100 comprises a sample detector 108 which detects digital code samples for past sample periods and the instant sample period. Past digital code samples are stored in a sample storage 114. Past digital code samples and the instant digital code sample are compared by a comparator 112. If the samples are equal, the signal path 102 is idle. If the samples are unequal, the signal path 102 is in use. It is contemplated that the past digital code sample substantially immediately preceding the instant digital code sample will be compared to the instant digital code sample.

Abstract: An improved surge protection circuit for withstanding surges is provided. A first node is provided for coupling to a tip lead, and second node is provided for coupling to a ring lead. The surge protection circuit has a first current path for turning on a first transistor, and a second current path for redirecting current from the remaining excess surge energy from one lead to the other lead. The first current path further includes a first sub-path to direct the initial voltage surge to the base electrode of the first transistor to cause the first transistor to turn on hard. The second sub-path redirects current from the initial excess surge energy from the voltage surge to a capacitor prior to the time before the first transistor is fully turned on, so as to protect the base-emitter junction of a second transistor from being reverse biased.

Abstract: A method for performing a speakerphone function in a cordless telephone contemplates the steps of: forming a speakerphone speech path to enable the speakerphone function in response to user input of a speakerphone key, detecting a busy tone signal received from a telephone line while the speakerphone speech path is formed, and automatically interrupting the speakerphone speech path to disable the speakerphone function in response to detection of the busy tone signal. The speakerphone speech path is automatically interrupted by controlling a hook relay to disconnect the telephone line from a voice processor that transmits and receives voice signals, and controlling an electrical switch to disconnect the voice processor from a microphone that generates the voice signals from a user's speech and a speaker that aurally transmits the voice signals received from the telephone line via the voice processor.

Abstract: A self-contained signaling and control device for detecting DTMF tones and generating a signal, such as an audible, visual, or control signal, upon detection of one or more predetermined DTMF tones includes an on/off-hook detection circuit coupled to a telephone line; a power supply circuit coupled to the on/off-hook detection circuit; a DTMF receiver circuit coupled to the power supply circuit; a logic circuit coupled to the DTMF receiver circuit; and a signal generator coupled to the logic circuit and the power supply circuit. The on/off hook detector circuit for detecting changes in voltage across a telephone line includes a circuit for detecting a voltage on the telephone line and a circuit for generating an enable signal in response to rapid changes in the voltage on the telephone line. The on/off hook detector circuit does not generate an enable signal in response to slow changes in the voltage on the telephone line.

Abstract: A computer integrated telephony system embodied in a PC that includes a telephony interface connected to the local loop that detects whether one or more extension phones are off-hook by using the signal generating and detection capabilities found on a typical telephony interface card. In the preferred embodiment, the telephony interface is based on a programmable DSP that generates and injects onto the local loop a subsonic signal having a known shape and amplitude. If one or more extensions are off-hook, the amplitude of the subsonic signal detected on the line will be significantly attenuated. The amplitude of the detected signal is compared against a threshold value and an indication is made if the detected signal amplitude is below the threshold value.

Abstract: Apparatus and method for generating user warning signal during data transmission suspension or degradation, that allows an user to identify that parallel operation of plain old telephone system (POTS) and digital data communications equipment is either occurring, or being attempted. More particularly, the user signal warning indicates the impact to the operation of a multiple channel data communications device as a result of the parallel operation with the POTS equipment. A multiple variable signal alerts the user to the parallel operation, the amount of degradation, the elapsed time of the degradation to data communications, and which user site is causing the degradation by the direction of the data traffic being impacted.

Abstract: The invention provides an apparatus for use with a subscriber line interface circuit in a telephone system, the subscriber line interface circuit being interposed between a telephone central office and a subscriber line, the subscriber line being coupled with a subscriber telephone device.

Abstract: Disclosed is a method for communication with no power feed in an exchange. (1) A calling subscriber unit transmits a special service code designating the disuse of a direct current loop together with the numeric information on the called subscriber unit to the exchange after formation of a direct current loop. (2) When the special service code is received, an on-hook transmission state in which the transmission and reception of an alternating current signal is possible between the subscriber line interface circuit and the calling subscriber unit even if no direct current loop is formed is established in the subscriber line interface circuit to which the calling subscriber unit which has transmitted the special service code is connected. (3) The calling subscriber unit disconnects the direct current loop, and the exchange maintains the speech path between the calling subscriber unit and the called subscriber unit even after the direct current loop is disconnected.

Abstract: In an arrangement for the connection of two or more terminals (1, 1') to one subscriber line (3) the terminals (1, 1') are connected to a chain so that the connection from the subscriber line (3) to a terminal (1) is further branched (13) to the next terminal (1'), and the arrangement according to the invention is characterized in that it comprises means (18, 20) to detect whether the terminal (1) and the next terminal (1') are in the operating state or in the idle state; a controllable switch (12, 14) for each terminal (1, 1') connected to the subscriber line (3) in order to connect the corresponding terminal (1, 1') to the subscriber line (3) and disconnect it from the line; and means (18, 20) to independently control the switch (12, 14) corresponding to each terminal (1, 1') depending on which states are detected for the terminals (1, 1'). Thus it is possible, when required, to cut off the current from the subscriber line (3) in order to disconnect the connection.

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: An inadvertent off-hook apparatus for use in a telephone system having a handset for automatically restoring an inadvertently off-hook telephone to an on-hook in order to receive an incoming call. The apparatus comprises a current sensing unit comprising a photo-coupler coupled to one of a tip and a ring terminal of the telephone line, for sensing variations of current of the telephone line in response to an incoming call and detecting a handset misplacement signal indicating that the telephone is in an inadvertent off-hook condition; and a control unit connected to the current sensor unit, for disconnecting the voice network from the telephone line to block the speech path in response to the handset misplacement signal, and for connecting the voice network to the telephone line to form the speech path to answer the incoming call.

Abstract: A combined loop current sink, battery detector, and ringing detector circuit as used in a channel unit at a telephone central office connection to a digital loop carrier circuit, to provide off-hook and on-hook signaling to analog switching circuits, and to simultaneously receive normal battery and ringing signals from the analog switching circuits. The combined circuit includes tip and ring connections to the digital loop carrier circuit to provide telephone service, a loop input controlled by logic circuits, at the telephone central office, and a battery output connected to the logic circuits. A first optocoupler, is connected to the loop input and also to ground, for providing a floating voltage coupling for the loop input to the circuit. A second optocoupler, is connected to the battery output and also to ground, for providing a floating voltage coupling for the circuit output. A transistor circuit has an input coupled to the first optocoupler and an output coupled to the second optocoupler.

Abstract: The present invention is directed to a control system which interfaces a plurality of telephones, referred to as extensions, to a central office telephone line. The control system includes a ring detector, a ring generator, a controller and a telephone extension bus. In accordance with one embodiment of the present invention, the control system is programmable to: (i) control the ringing function of a plurality of extensions when an incoming call is received; (ii) control the staging of the ringing function of a plurality of extensions when an incoming call is received; (iii) control the use of one or more of a plurality of extensions to initiate an outgoing call; (iv) control the use of one or more of a plurality of extensions when another extension is in-use, i.e. presently being used to engage in an ongoing telephone call; (v) control the use of one or more of a plurality of extensions when another extension is being used for a data call, i.e.

Abstract: A ringtrip detector comprises a reference counter for controlling a battery current generator, which shapes the ring signal, a zero pass detector for detecting zero passes in a voltage at a node, which is proportional to the telephone line current and two other counters. The zero passes of the voltage create a pulse at both the positive and the negative zero crossing of the zero pass detector. The reference counter is gated into a memory, when these pulses appear. The zero passing of the previous and the present ring cycle are stored in the memory. A counter decides the difference between the previous and the present ring cycles zero passes. If the zero pass difference between the present and previous ring cycles is greater than a fixed value, the output will indicate a "phase difference" and if it is less than the fixed value it will indicate "no phase difference".

Abstract: A signal-processing method and system for a telecommunications switch that supports a number of individually addressable telephones including transmitting ring signals to telephones that are determined to be in an inadvertent off-hook condition. The telecommunications switch is configured to transmit a first notification ring signal upon detecting that a particular telecommunications line is in a condition that indicates that the associated telephone is in the inadvertent off-hook condition. The first ring signal induces a ring condition that preferably is uniquely identifiable as indicating that the phone has been left off-hook. A second notification ring signal is transmitted if the phone is returned to the on-hook condition and an incoming call is directed to the telephone. Preferably, the second ring signal induces a uniquely identifiable ring condition indicating that an incoming call is directed to an off-hook telephone.