Abstract: Electrical equipment includes a housing having a hole formed therein; a microphone positioned inside the housing and in the proximity of the hole; a loudspeaker; emitter means arranged to emit an emitted detection sound signal via the loudspeaker; and processor means arranged to acquire a received detection sound signal via the microphone, to detect in real time from the received detection sound signal whether a user's finger is or is not positioned on or in the immediate proximity of the hole, and if a finger is positioned on or in the immediate proximity of the hole to cause a predetermined action to be performed.

Abstract: An apparatus for providing a connection to a wide area network for voice calls includes a wide area network circuit configured to transmit voice call data packets, a phone connection circuit configured to receive a voice call signal from a phone, a processor circuit configured to generate voice call data packets based on a voice call signal received by the phone connection circuit and a power management circuit configured to switch off at least a part of the apparatus to reach a power down mode of the apparatus, if a supply voltage drops below a supply voltage threshold.

Abstract: A communication system for current-modulated transmission of data via a current loop—into which a master device and at least one slave device are looped. The at least one slave device has a switching means that is actuable by an evaluation and control unit and that is configured to short a current loop in the closed state, wherein the evaluation and control unit is configured to temporarily close and then reopen the switching means during a system configuration detection phase. An evaluation and control unit of the master device—is configured to detect when the at least one slave device is looped into the current loop.

Abstract: Caller feedback in mobile devices, in which, upon receiving a telephone call from a caller, a user selection of a control is detected, and a message associated with the selected control is determined and automatically transmitted to the caller.

Abstract: A reverse power feeding power PSE in electrical communication with a power source and a DPU, the PSE constituted of: a power output terminal; and a control circuitry, the control circuitry arranged to: output at the power output terminal power from the power source, the output power exhibiting a voltage within a predetermined operating range, after a predetermined inrush time period from an initial output time of the power, determine the magnitude of current flowing through the power output terminal, responsive to the determined current magnitude being greater than a predetermined current draw value, cease the power output.

Abstract: An automatic call blocking and routing system. The system includes input and output ports, a telephone line interface and an off-hook circuit in communication with the input port, an output port, a switch in communication with the input and output ports, memory, a user-operable control, and a microprocessor responsive to the user-operable control to store in the memory data indicative of blocked callers. The microprocessor is responsive to an incoming call to compare the stored data with caller ID data in the incoming call. If the caller ID data matches a blocked caller, the microprocessor blocks the call by causing the off-hook circuit to send an off-hook signal to the input port, waiting a predefined interval of time, and then causing the off-hook circuit to send an on-hook signal to the input port.

Abstract: A redriver device is provided to receive signals from a first device and forward the signals to a second device on a differential link. Detection circuitry is provided to detect presence of the second device on the link by detecting a pulldown voltage generated from termination of the second device on the link, and pulldown relay circuitry is provided to generate an emulated version of the pulldown voltage of the second device on pins to connect to the first device in response to detecting presence of the second device on the link.

Abstract: Embodiments disclose a base of a cordless digital telephone set and a cordless digital telephone set. In the base of a cordless digital telephone set, a subscriber circuit module and a Bluetooth module can establish, under control of a main control module, a communications channel for direct interconnection, thereby reducing workload of the main control module, and optimizing a transmission path of voice data. The base of a cordless digital telephone set in embodiments of the present invention includes a switch module. When receiving a first control signal that is sent by the main control module, the switch module connects a communication data output pin of the subscriber line interface circuit module to a communication data input pin of the Bluetooth module; and connects a communication data input pin of the subscriber line interface circuit module to a communication data output pin of the Bluetooth module.

Abstract: A method and an apparatus are provided. The apparatus comprises a power source node; a light-emitting diode; a full-wave rectifier configured to produce unipolar half-waves from an alternative current mains supply connected to the power source node; and a voltage controlled switch configured to drive the light-emitting diode with pulses, each pulse derived from a half-wave, the width of the pulses being inversely proportional to mains supply voltage.

Abstract: A communication control device for controlling communication performed over a communication line includes a voltage-value acquirer for acquiring a value of a line-to-line voltage of the communication line in an on-hook state, a first determiner for determining whether the voltage value is continuously equal to or lower than a threshold voltage for a first predetermined duration, a current-value acquirer for acquiring a value of a current flowing through the communication line in an off-hook state when the voltage value is continuously equal to or lower than the threshold voltage for the first predetermined duration, a second determiner for determining whether the current value is continuously equal to or smaller than a threshold current for a second predetermined duration, and a disconnection determiner for determining that the communication line is disconnected when the current value is continuously equal to or smaller than the threshold current for the second predetermined duration.

Abstract: According to embodiments described herein, a circuit includes an interface circuit configured to be coupled to a transducer and a detection circuit. The interface circuit is configured to provide a digital output signal to a signal input terminal of a processing circuit. The detection circuit is configured to receive the digital output signal and provide a low power enable signal to a low power enable terminal of the processing circuit. In the various embodiments, the digital output signal is based on a transduced signal from the transducer and the low power enable signal is determined by comparing the digital output signal with a first threshold.

Abstract: As taught herein, a floating current source outputs a load biasing current from a source terminal into an external load which may have a variable resistance, and sinks the load biasing current from the load into a sink terminal. Advantageously, the floating current source includes a single-transistor current sink having a bias control that sets the magnitude of the load biasing current desired, and further includes a single-transistor current source that self-biases from the float voltage developed on the external load to an operating point at which the single-transistor current source sources the desired magnitude of load biasing current. One or more AC shunts within the self-biasing network prevent any AC fluctuations present or impressed on the source terminal of the floating current source from changing the operating point of the single-transistor current source, thereby imparting a high effective impedance to the single-transistor current source.

Abstract: A powering arrangement for use with reverse power feeding arranged to detect an improperly connected POTS phone going off-hook by: measuring a first current flow from a power sourcing equipment; identifying a rapid first increase in current flow from the measured first current flow, the rapid increase defined as a rate of change greater than a predetermined minimum rate of change; identifying a second increase in current flow from the measured first current flow, the identified second increase greater than a predetermined minimum amount; confirming that the identified second increase in current flow is maintained for at least a predetermined amount of time beginning with the identified first increase in current flow; and outputting an error signal to the power sourcing equipment in the event of the identified condition.

Abstract: A Line Interface Unit (LIU) can communicate a number of electromagnetic waveforms consistently fitting into a variety of specific waveform masks, such as masks defined by ITU-T G.703. The LIU includes a transmit part that includes a feedback controller that facilitates the LIU outputting electromagnetic waveforms consistently fitting into the specific waveform masks. The feedback controller can compensate for changes in environmental conditions, such as supply voltage, line profile, line impedance per protocol, doping gradient, and temperature. Also, this feedback controller allows for avoiding constant hardware modifications to the LIU for adjusting to different protocols or masks. It also can enable the LIU to instantiate a great number of times, such as twenty-one times on the same die, where the transmit part performs the feedback controller independently for each instantiation.

Abstract: A method and an apparatus for reducing current consumption in a mobile terminal are provided. The mobile terminal includes a power supply unit for outputting a paging power signal that repeats power on and off states and a microphone bias according to a paging period previously set by a network, a connection unit for connecting the peripheral device and for outputting a connection detecting signal when connection of the peripheral device is detected, a determination unit for receiving the paging power signal and the connection detecting signal as an input signal and for generating and outputting a microphone bias apply signal when a power on state of the paging power signal is detected, and a controller for controlling application of the microphone bias apply signal to the connection unit when the controller receives the microphone bias apply signal.

Abstract: A novel and useful apparatus for and method of packet detection and carrier frequency offset estimation. The packet detection mechanism is robust to channels and sustains reasonable miss-detect (and false alarm) rates at low SNR values. The mechanism uses a modified combined cross correlation and delay and correlate scheme. A delay and correlate scheme is used in order to handle the effects of multipath while swapping integration and multiplication to increase cross-correlation factors resulting in improved sensitivity in low SNR conditions. Correlation is divided into multiple chains to generate a plurality of partial correlations to observe short patterns in the spread sequence resulting in improved performance in long multipath channels.

Abstract: A communication apparatus has an off-hook detection function, and has a first electric power supply for supplying electric power to a telephone control unit for controlling a telephone apparatus, and a second electric power supply for supplying electric power to an off-hook detection unit for detecting an off-hook of the telephone apparatus. The apparatus causes the off-hook detection unit to detect an off-hook of the telephone apparatus when, from a first power mode, a second power mode, in which electric power consumption is less than in the first power mode, is transitioned into.

Abstract: A cordless telephone system provides indication of event information for customer premises equipment. The cordless telephone system includes a base station and handsets. The base station receives event information from the CPE. The base station transmits the event information to a handset, and the handset provides an indication of the event information to a user.

Abstract: In one embodiment, a low cost, simple circuit for detecting an off-hook condition of a telecommunication line comprising tip and ring signal lines is provided. The circuit comprises a voltage divider for coupling between the tip and ring lines without an intervening transistor and having a node at which is presented a scaled version of a voltage across the voltage divider. The circuit further comprises a transistor having a control terminal coupled to the node, a first current flow terminal coupled to a voltage source, and a second current flow terminal coupled to an output terminal, wherein the output terminal bears a value that is indicative of a voltage across the tip and ring lines and thus whether the telecommunication line is off-hook.

Abstract: A device containing an MTA, executing a connection deletion method, determines that a connection at one of its endpoints may be abandoned after a predetermined amount of time after an on-hook event following a first call. If the MTA determines that the CMS it is coupled to has begun managing a new, or second, call, the MTA, sends a message to the CMTS it is coupled to requesting deletion of the first call, and the resources associated with it. The MTA also sends a message to the CMS requesting deletion of the connection at the endpoint of the MTA device.

Abstract: A communication apparatus, which is connected to a phone line, and to which an external telephone is connectable to. The communication apparatus includes: a line-voltage detecting unit which detects a line voltage; a communication-signal detecting unit which performs detection on a communication signal, which is input to the communication apparatus from the phone line or from the external telephone upon the external telephone is hooked up; and a control device which performs a hook-up determining process of determining that the external telephone is in a hook-up state when the line voltage detected by the line-voltage detecting unit is equal to or less than a first threshold value and the communication signal is detected by the communication-signal detecting unit.

Abstract: Disclosed is a three-way call detection system and method for use with a telephone management system. Specifically, a three-way call detection system and method for detecting continuous noise indicative of an attempt to mask a three-way call attempt. The continuous noise detection system and method may be stand alone or used in conjunction with any existing three-way call detection system and method.

Abstract: A telephone system comprising switching circuitry configured for coupling a call to a telephone extension coupled to the system, voice processing circuitry configured for automatically interacting with the call, a microprocessor, a first data bus connected between the microprocessor and the switching circuitry, and a second data bus connected between the microprocessor and the voice processing circuitry.

Abstract: A communication terminal devicecapable of being connected with an external telephone and of receiving and transmitting facsimile data from and to a network, includes: an off-hook detector configured to detect an off-hook condition of the external telephone, an semiconductor DAA (Data Access Arrangement) including an impedance switcher configured to switch impedances and a direct-current resistance switcher configured to switch direct-current resistances; an impedance switching controller configured to instruct the impedance switcher to switch the impedances; a direct-current resistance switching controller configured to instruct the direct-current resistance switcher to switch the direct-current resistances, wherein, when the off-hook detector detects the off-hook condition of the external telephone, the impedance switching controller instructs the impedance switcher to switch the impedances and the direct-current resistance switching controller instructs the direct-current resistance switcher to switch the d

Abstract: This invention provides a communication apparatus, which suppresses abrupt changes of a current and voltage generated in a communication line upon connecting an external telephone to the communication line, and a control method thereof. To accomplish this, in a communication apparatus of this invention, when an off-hook state of an external telephone is detected upon connecting the external telephone to a communication line, an SOC captures a line using a first line capture means having an impedance lower than the external telephone side, and then switches an H-relay to connect the external telephone to the communication line. Furthermore, the SOC temporarily switches a line capture state to a second line capture means having an impedance higher than the first line capture means after the H-relay is switched and before the line is released.

Abstract: In one embodiment, a low cost, simple circuit for detecting an off-hook condition of a telecommunication line comprising tip and ring signal lines is provided. The circuit comprises a voltage divider for coupling between the tip and ring lines without an intervening transistor and having a node at which is presented a scaled version of a voltage across the voltage divider. The circuit further comprises a transistor having a control terminal coupled to the node, a first current flow terminal coupled to a voltage source, and a second current flow terminal coupled to an output terminal, wherein the output terminal bears a value that is indicative of a voltage across the tip and ring lines and thus whether the telecommunication line is off-hook.

Abstract: An apparatus includes a DSL transceiver configured to transit to a DSL wait state in which a power transmitted from the DSL transceiver to a local-end line is substantially reduced in response to an interruption or substantial stop at the DSL transceiver of reception of DSL communications from the local-end line. The DSL transceiver is configured to transmit to the local-end line a DSL acknowledge signal in response to receiving from the local-end line a DSL wait signal. The DSL transceiver is configured to resume to transmit DSL communications to the local-end line at a power substantially higher than the power transmitted thereto in the DSL wait state in response either to receiving from the local-end line DSL transmissions at a substantially higher power than received there from in the DSL wait state or to receiving from the local-end line a second DSL acknowledge signal.

Abstract: A line control apparatus having a first interface for connecting to a telephone line, a second interface for connecting to a facsimile apparatus, and a third interface for connecting to a telephone, includes: a first detecting unit that detects a calling signal transmitted from the telephone line and a second detecting unit configured to detect a signal from the telephone line, such signal having a voltage lower than a voltage that the first detecting unit can detect. In accordance with the second detecting unit having detected a signal from the telephone line, the control unit switches from a state wherein the first interface and the third interface are connected to a state of not being connected.

Abstract: Various techniques are provided to detect a state of a communication signal. In one example, a method of detecting a state of a signal includes receiving a differential communication signal comprising a positive portion and a complementary negative portion. The method also includes generating a common mode voltage signal from the positive portion and the negative portion of the communication signal. The method also includes rectifying the positive portion and the negative portion of the communication signal to provide a rectified signal. The method also includes comparing the common mode voltage, signal with the rectified signal. The method also includes generating a high frequency detect signal in response to the comparing. The method also includes determining whether the communication signal is in an idle state or a high frequency state based on the high frequency detect signal.

Abstract: An HVAC unit includes a transformer and a system controller. The transformer is configured to receive power from a first and a second phase of a three-phase power source and to produce a first reduced-voltage waveform therefrom. The system controller is adapted to sample the reduced voltage waveform to determine a figure of merit of the three-phase power source. The controller is further configured to operate the HVAC unit in response to the figure of merit.

Abstract: Embodiments of this disclosure include methods in which a three-way call attempt is detected. Methods include monitoring the active communications of a telephone management system for pulses of energy indicative of a three-way call. A Fast Fourier Transform (FFT) is computed for each pulse of energy with time domain characteristics consistent with a click. Phases of each component for the pulse are also analyzed. If the phases are generally linear (i.e., if the phases have a common group delay or phase delay), then the pulse is a three-way call click and appropriate action (e.g., monitoring the call, terminating the call, warning the caller, etc.) is initiated.

Abstract: The invention relates to a method for detecting the status of a telephone receiver (H) for a communication terminal (EG), wherein the telephone receiver (H) is equipped with a microphone (M) and with a loudspeaker (LS). The loudspeaker (LS) of the telephone receiver (H) is used to output a defined tone signal, and this tone signal is simultaneously picked up again by means of the microphone (M) of the telephone receiver (H). The tone signal picked up is analysed, with at least one value for at least one parameter of the tone signal picked up being ascertained, and the at least one value is used to determine the status of the telephone receiver (H).

Abstract: A method and loop qualification unit for determining loop parameters of a topology of a twisted pair loop for a digital subscriber line system. The parameters are represented by a vector that receives a measurement of a SELT parameter measured at one end of the loop and a measurement of a DELT loop transfer function measured at both ends of the loop. A first model generator generates a first model for the SELT parameter and a second model generator generates a second model for the DELT function based on the loop parameters represented by the vector. A processor then determines the parameters by minimizing the differences between the first model and the SELT parameter, and the second model and the DELT function. The determined parameters are represented by the vector that provides the minimization.

Abstract: In one embodiment, the present invention includes an apparatus having a first pair of low voltage operational amplifiers to generate an output representative of an absolute value difference of first and second line voltages of a subscriber loop, and a third low voltage operational amplifier having an input coupled to the output of the first pair of low voltage operational amplifiers to filter the output and to provide a switch control signal for a switching regulator that provides a voltage used to generate the first and second line voltages. The apparatus may include additional circuits such as a limit circuit to limit the input to the third low voltage operational amplifier and one or more speedup circuits to reduce a filter time constant of the third low voltage operational amplifier during a ringing mode of the subscriber loop.

Abstract: Embodiments for connecting and disconnecting a first pair of conductors of a jack from a second pair of conductors of the jack, the first pair of conductors configured to connect to a first line and the second pair of conductors configured to connect to a secondary line, detecting a voltage or a current on the secondary line while the second pair of conductors is disconnected from the first pair of conductors, and notifying a user in response to detecting the voltage or the current on the secondary line while the second pair of conductors is disconnected from the first pair of conductors are disclosed.

Abstract: A VOX interface is provided that interfaces with at least two communication paths to two separate devices. One communication path may be to a first electronic device, such as a central monitoring station remote from the VOX interface, and another communication path may be to one or more remote devices, such as to one or more patient devices remote from the VOX interface. The VOX interface may determine which of the communication paths is sending a signal (such as an audio signal), and configure the VOX interface (via one or more switches) to pass the signal through. Specifically, the VOX interface may sense signals indicating the presence of audio from a central station audio bus and the patient station bus, may do some background noise filtering on the signals, and may pass these filtered values through a differentiator circuit to determine which bus presented the audio.

Abstract: In one embodiment, a low cost, simple circuit for detecting an off-hook condition of a telecommunication line comprising tip and ring signal lines is provided. The circuit comprises a voltage divider for coupling between the tip and ring lines without an intervening transistor and having a node at which is presented a scaled version of a voltage across the voltage divider. The circuit further comprises a transistor having a control terminal coupled to the node, a first current flow terminal coupled to a voltage source, and a second current flow terminal coupled to an output terminal, wherein the output terminal bears a value that is indicative of a voltage across the tip and ring lines and thus whether the telecommunication line is off-hook.

Abstract: The invention provides a low cost, simple, circuit for detecting the condition of a telephone line.

Abstract: A telephony distribution system includes a plurality of terminals with two connection points (16A), each for one pair of conductors (17A) forming part of a telephony distribution installation, and, for each of those terminals (16A), a short-circuit manager (25) including a substitution current source (26), a switch (27) and control means (28-31) for causing the switch (27) normally to assume a position in which its output terminal (34) is connected to an input terminal (32) itself connected to a pair of conductors (13, 15) providing a telephone line and to cause the switch (27). In the event of a short-circuit between the two connection points of the terminal (16A) concerned, to assume a second position in which that terminal is connected to the auxiliary current source (26).

Abstract: This invention provides a communication apparatus, which suppresses abrupt changes of a current and voltage generated in a communication line upon connecting an external telephone to the communication line, and a control method thereof. To accomplish this, in a communication apparatus of this invention, when an off-hook state of an external telephone is detected upon connecting the external telephone to a communication line, an SOC captures a line using a first line capture means having an impedance lower than the external telephone side, and then switches an H-relay to connect the external telephone to the communication line. Furthermore, the SOC temporarily switches a line capture state to a second line capture means having an impedance higher than the first line capture means after the H-relay is switched and before the line is released.

Abstract: In one embodiment, a tone event detector first determines whether the presence of a tone is indicated on the input signal, and then, based on this determination, selectively determines whether a tone has been detected on the input signal. For example, in one embodiment, tone detection is performed only when the presence of a tone is first indicated, such that if the presence of a tone is not indicated, tone detection need not be performed. This may help reduce complexity of a tone event detector since a simplified method may be used to indicate the presence of a tone, and the more complex algorithms for tone detection may be enabled only when needed. Also, in one embodiment, detection of a tone includes generating one or more tone characteristics corresponding to the detected tone which may then be used to determine whether the detected tone corresponds to a valid tone event.

Abstract: The invention relates to a method for detecting the status of a telephone receiver (H) for a communication terminal (EG), wherein the telephone receiver (H) is equipped with a microphone (M) and with a loudspeaker (LS). The loudspeaker (LS) of the telephone receiver (H) is used to output a defined tone signal, and this tone signal is simultaneously picked up again by means of the microphone (M) of the telephone receiver (H). The tone signal picked up is analysed, with at least one value for at least one parameter of the tone signal picked up being ascertained, and the at least one value is used to determine the status of the telephone receiver (H).

Abstract: A multifunction device previously stores a line connection condition of when a line interface received caller ID information in an EEPROM, and determines that a line with an exchange is connected based on a first ringing signal or a second ringing signal. When it is determined based on the first ringing signal that a line connection is a first type of connection, the line is connected according to the line connection condition. On the other hand, when it is determined based on the second ring signal that a line connection is a second type of connection, the line is connected using a line connection condition, which is adjusted by an adjustment device at the time of determination.

Abstract: An apparatus and method for controlling telecommunications is provided. The apparatus, which in one embodiment is a switch, may be connected between a computer-telephony integrated (CTI) workstation and multiple communication lines to elements such as Central Offices. The switch may be manipulated either manually or by the CTI workstation to connect to one of the multiple communication lines.

Abstract: A main terminal and a method of operating the same. In this method of operating the main terminal, the main terminal is connected to a telephone network so as to communicate with the telephone network, and selectively connects an external terminal to the telephone network. To perform the method, first, if it is requested that the telephone network be disconnected from the external terminal and instead be connected to the main terminal, an internal current to flow into the main terminal is obtained from a loop voltage generated when the external terminal is in connection with the telephone network. Next, the internal current is applied to the main terminal. Thereafter, the telephone network is disconnected from the external terminal and instead connected to the main terminal. While the internal current is flowing in the main terminal, the main terminal maintains the loop voltage generated when the external terminal is in connection with the telephone network.

Abstract: Method, including monitoring an audio signal on a telephone line with a detector and detecting an energy pulse in the audio signal on the telephone line; processing the energy pulse with a processor, where the energy pulse comprises a plurality of frequency components; determining a length of the energy pulse on the telephone line; calculating a phase for each of the plurality of frequency components to generate a plurality of phase values; generating a signal if the plurality of phase values are linear and if the length of the energy pulse is less than 40 milliseconds, where the signal is indicative that the plurality of phase values are linear and that the length of the energy pulse is less than 40 milliseconds, and further indicative that the signal is a three-way call attempt on the telephone line; and transmitting the signal to a host computer.

Abstract: A method and apparatus for detecting the presence and the type of network devices connected to a management device via transmission lines. The apparatus may include a pull-up resistor, a pull-down resistor, a filter, and a presence detector, the resistors superimposing a DC or low-frequency voltage on the transmission line. The impact, if any, of the DC voltage one communications equipment and circuitry can be reduced by a coupling that isolates the DC voltage. Similarly, the filter prevents transmitted data signals from interfering with the DC voltage level. The method and apparatus function regardless of whether the network device is functional or powered on, and different values of pull-up or pull-down resistors can be used to indicate the type of device that terminates the transmission line.

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 a desired frequency range due to the customer's terminal equipment from an ADSL a DSL 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: The telephone line coupler circuit has a single transmit opto-coupler whose output includes a DC bias component connected to a gate of a line seize switch for connecting a DC line seize load across the ring and tip contacts of the telephone line. The line seize switch is saturated by the transmit opto-coupler bias output and the AC component of the transmit opto-coupler output is sent over the telephone lines. The receive opto-coupler is used both for receiving communications signal and for detecting the ring signal. The band pass filter connected to the output of the receive opto-coupler may be switched to pass a ring signal frequency band or a communications frequency band. The circuit operates using two opto-coupler devices while conventional circuits require four opto-coupler devices.

Abstract: The invention herein is fallback function communications device comprised of a microprocessor, utilized to perform a predetermined operation and processing of a predetermined input signal and then output a corresponding signal, as well as a minimum of one relay circuit having an amplifier circuit and a relay. The terminal at the first side of the relay is connected to the telephone line tip/ring terminal, while the terminal at the second side of the relay is connected to the Public Services Telephone Network (PSTN) tip/ring terminal of the microprocessor. An off-hook detection circuit is connected to the PSTN tip/ring terminal and also connected to the ring detection terminal of the said microprocessor. A dummy load circuit is connected to the tip terminal and the ring terminal of the PSTN. As such, in the event of Voice Over Internet Protocol (VOIP) system failure, the present invention is capable of automatically switching to the PSTN and thereby maintain telephone system operation.