Abstract: A telephone interface system is inserted between the telephone handset and base to provide automatic switching between voice and data modes of communication. The interface includes a modem having a receive port coupled to the telephone base speaker lines and a transmit port switchably coupled to the base microphone lines, a switch for selectively coupling the telephone handset to the base, and a processor for monitoring data received by the modem and controlling the switch to automatically decouple the telephone handset from the base when data is being received or transmitted by the modem. The modem includes a tone generator that generates a predetermined start signal to signal a remote unit at the other end of the communication link to enter data mode prior to transmission of data. Similarly, the modem includes a tone detector to detect a start signal sent by the remote unit that causes the unit to switch into data mode in preparation for receiving data.

Abstract: A subscriber module (40) for a network interface device (10) having a jack (100) defining a plug-receiving cavity (102) thereinto, and having a plug (50) insertable into the jack. The plug includes a plurality of interconnecting contacts (56) disposed at a mating end (58) thereof, and the jack includes first and second contacts (106,112) secured within the plug-receiving cavity in spaced-apart disconnected pairs. Insertion of plug (50) into jack (100) moves interconnecting contacts (56) between associated ones of first and second contacts (106,112) to electrically interconnect them, completing otherwise unconnected circuits between the distribution cable and the subscriber premise wiring. Preferably plug (50) includes a sealing member (74) therearound to seal the mating interface when plug (50) is inserted into jack (100).

Abstract: This invention discloses a telephone network interface enclosure comprising a telephone company compartment and a telephone subscriber compartment. Disposed within the telephone company compartment is a metal grounding strip. There is a network termination module disposed within the telephone network interface enclosure. The network termination module is partially disposed in both the telephone company compartment and the telephone subscriber compartment. The network termination module contains a protector element, subscriber terminals and a means for grounding. The subscriber terminals are located in the telephone subscriber compartment. The means for grounding is located in the telephone company compartment. and is connected to the metal grounding strip.

Abstract: A test system directed to apparatus for transmitting and receiving multiple telephone transmission signals over a single twisted pair. The system converts an analog signal from a local switching station to an 80 ksymbols/sec signal for transmission over a twisted pair by a line card. A remote terminal converts the 80 ksymbols/sec signal back into a conventional analog signal for use in conventional telephone, facsimile or other related equipment. The test equipment separately tests the entire system, the line card portion of the system, the remote terminal portion of the system, and the twisted pair.

Abstract: A headset amplifier, adapted for use with a voltage source such as a battery, includes a time-out-timer circuit for deactivating the headset amplifier after a first predetermined period of time and for reactivating the amplifier in response to a signal fed to an input port of the time-out-timer circuit.

Abstract: A telecommunications signalling interface for computer systems is presented. Control and information signals from the telephone switch are received, decoded, and converted to a standard interface format for retransmission to the computer. Control and information signals from the computer are received and converted to a standard format for transmission to the telephone switch. The power supply for the device may be derived from the telephone network and the computer interface.

Abstract: A system and method of synchronizing visual indicators in digital telephone including at least one attached auxiliary device. Visual indicators on the base telephone and the auxiliary device are first set to an initial state. Later, as various telephony features are activated, corresponding ones of the visual indicators on the base telephone and the auxiliary device are operated at predetermined cadences. When the cadence control mechanism (and thus the visual indicators) of the base telephone reaches a predetermined state, a state machine in the base telephone sends a synchronization message to the auxiliary device and then continues to operate the visual indicators on the base telephone at their predetermined respective cadences. Upon receipt of the synchronization message, the auxiliary device sets its cadence control mechanism to the predetermined state, thus synchronizing them with their like cadence counterparts in the base digital telephone.

Abstract: This invention discloses a network termination module which comprises a base structure having a means for grounding. Mounted on and above the base structure are a pair of insulation displacement terminals, a telephone jack and subscriber terminals. The insulation displacement terminals are electrically connected to the telephone jack. The network termination module also includes an openable cover which, in its closed position, establishes electrical connection between the insulation displacement terminals and the subscriber terminals, and, in its open position, breaks the electrical connection between the insulation displacement terminals and the subscriber terminals. The cover, in its closed position, also closes off access to the jack and to the subscriber terminals. Disposed within the base structure is a protector element which is electrically connected to the insulation displacement terminals. The protector element is also electrically connected to the means for grounding.

Abstract: A digital telephone for use as a PBX station includes a display for displaying information such as called number and call duration as well as messages from other stations or from a message center associated with a PBX system. The station includes a printer mechanism having the capability to print information corresponding to what is currently displayed on the display as well as messages from other stations or from the message center. Provision of the printer enables a hard copy printout of messages and calling information to be obtained.

Abstract: A telephone jack includes a first pair of contact wires for connection to a subscriber premises line and a second pair of contact wires for connection to an incoming telephone company line, a pair of bridging members are mounted for insertion in the jack and into engagement with the first and second pairs of contact wires to interconnect the subscriber premises line and the incoming telephone company line and are for being withdrawn from the jack and from engagement with the first and second pairs of contact wires to disconnect the subscriber premises line from the incoming telephone company line to provide a demarcation point therebetween.

Abstract: An alphanumeric caller identification telephone is disclosed which has several advantages and novelties. Among them are that when certain predetermined incoming calls including a number or name are received, this apparatus can display not only the received number, but can also spell, speak or display the name of the caller. In addition, this apparatus can be set to ring, alert or even activate a plurality of control outputs when certain incoming calls including a number or name are received. The activation of alarm(s) and control output(s) can also be set during a predetermined time interval only. Furthermore, this phone has an infrared transmission system, which can transmit recorded data between units.

Abstract: A telephone privacy protector for connection to a common exchange line and each one of at least two telephone operated devices sharing a line includes a voice connecting circuit for connection between a respective telephone line operated device and the line. There is a control deice connected to the circuit having an on and off state wherein the control device in the on state permits the voice connecting circuit to operate. There are means for turing the control device on when the respective telephone line operated device goes off hook provided that no other telephone line operated device sharing the line is off hook. There are means for providing a residual charge to the control device in order to reactivate same after the respective telephone line operated device is placed momentarily on hook and then returned to an off hook state while any other telephone line operated device connected to the line is off hook.

Abstract: A ringer assembly which is used in conjunction with a telephone system. The ringer assembly is especially useful for hearing impaired individuals although not limited thereto. The ringer assembly includes a unique housing for mounting the ringer apparatus so as to improve and enhance the acoustical operation thereof.

Abstract: A transmission control unit for controlling transmission and reception of data between electronic devices via a telephone without any use of acoustic coupling is disclosed. The transmission control unit is equipped with a first terminal for detachably connecting a main body of the telephone, a second terminal for detachably connecting a handset removable from the main body of the telephone, and a third terminal for detachably connecting the electronic device. When the main body, the handset and the electronic device are, respectively, connected to the first, second and third terminals, the transmission control unit permits analog electronic data from the electronic device to be input to the main body of the telephone at the handset interface level, and permits analog electronic data from the main body to be sent to the electonic device.

Abstract: An interface unit for interconnecting a telephone central switch to a personal computer. The interface unit receives power and data from the switch over a two wire twisted pair. The data is in a half duplex T.C.M. format and is transformed into standard digital data with the logic "1" and "0" being represented by +5V and 0V respectively. The standard digital data is then arranged into 8 bit words and encoded in either an asynchronous or synchronous manner depending on the type of computer. The interface unit has a line interface circuit which provides the physical interface between the interface unit and the computer. The interface unit has a transmitter circuit which converts the +5V and 0V digital signals to -5V and +5V, respectively. These values are recognized by the computer as logic "1" and "0".

Abstract: An entrance terminal and interface between the telephone company network and the subscriber's premises is more readily serviced by a single module having an enclosed printed circuit board combining the voltage overload device, the demarcation plug and socket and a service circuit such as a half-ringer or maintenance termination unit.

Abstract: A control circuit for an electrical telephone accessory detects if the telephone receiver is on the cradle, the telephone ringer is actuated, or if the telephone receiver is lifted from the cradle. The control circuit connects the electrical telephone accessory to a power supply source when the telephone ringer is actuated or when the telephone receiver is lifted from the cradle.

Abstract: A telephone network interface device comprises a base structure, a protector assembly disposed within the base structure and a cover on the base structure. The device also includes a telephone jack and terminals to which a telephone subscriber's wiring can be connected. The combination of the base structure, cover, telephone jack and terminals comprise a stand-alone unit which can be mounted in a variety of enclosures when installed at a telephone subscriber's premises.

Abstract: An ISDN terminal adapter having a diagnostic function includes a terminal adapter section, an S/T pointer interface section, a D channel control section, a sub-address identifying section, and a remote monitor section. The terminal adapter section has a data rate converting function for communication with a terminal of a distant station connected to an ISDN. The S/T point interface section converts an output signal from the terminal adapter section into a protocol of the ISDN. The D channel control section receives D channel information from the distant station through the S/T point interface section and extracts a sub-address from the D channel information. The sub-address identifying section determines whether the sub-address of the D channel information input from the D channel control section coincides with a predetermined code.

Abstract: An enclosure for terminal blocks for interconnecting conductors of multiconductor cables includes provision for two or more terminal block modules. A lid is pivotably hinged to a box-like base section, with the base section including front and rear walls extending upwardly from a floor, and side walls extending downwardly from a transverse section of the lid into the open regions between the front and rear walls of the base section when the lid is pivoted to its closed position. When the enclosure is mounted vertically the lid is pivotable to an open position overcentered to remain open unassisted. The side walls include ribs having projections which engage upper edges of ridges extending upwardly from side edges of the floor between the front and rear walls, thus camming the lower edges of the side walls inwardly tightly against outwardly facing surfaces of the ridges for sealing.

Abstract: A telephone terminal disconnect accessory device for automatically disconnecting or hanging up the telephone at a first telephone terminal station when it is desirable to hold a conversation at a second telephone terminal station without having to return to the first telephone terminal station where the telephone was answered or from which a call was made, the device comprising a housing having at least two female modular jacks disposed in the walls thereof, and including an on/off switching means, a variable timing means, a latching relay means, a re-set switching means, and a transistor battery power supply.

Abstract: An apparatus for "hands off" control of a Voice Mail System over a telephone line by a user to allow the user to simultaneously perform other functions such as manually processing the "oral mail" to take notes, do data entry or the like. The apparatus includes a foot pedal that is wired with switches. The foot pedal switches are connected through an interface circuit to a DTMF tone generator or a generator of digital signals corresponding to VMS functions. The interconnection is such that depending upon the pedal activated a different tone or digital signal will be generated. The user can readily reconnect the interface to vary the signal to pedal correspondence for changes in Voice Mail Systems or to implement other Voice Mail System commands. The DTMF tone generator is connected in series between the hand set and base set of a telephone so that system can be readily connected to an existing telephone and so that the tones can be sent over the phone line to a Voice Mail System.

Abstract: An identifying telephone controller system using a main computer component with a central processing unit coupled to an in-house AC wiring system and utilizing a plug-in ringer/appliance controller receive and a base-remote telephone system to provide multi-function telephone operations including caller identification and call patching and remote appliance control.

Abstract: In a telephone system, several telephone terminals are connected to a single telephone line including several telephone interface circuits (6, 7, 8), each interface circuit being energized by ringing signals appearing on the line and being arranged between the telephone line (3) and one of the telephone terminals (13, 14, 15, 16), the ring of which is disconnected from the line. Each interface circuit comprises a circuit (26) for counting ringing signals and picking up the line, this first circuit receiving at the input the ringing signals appearing on the line (L1-L2) during a telephone call, and counting a predetermined number of these ringing signals, then picking up the line by a relay (27) at the moment the last ringing signal counted stops. The system is powered only by the signals on the telephone line.

Abstract: A telecommunications signalling interface for computer systems is presented. Control and information signals from the telephone switch are received, decoded, and converted to a standard interface format for retransmission to the computer. Control and information signals from the computer are received and converted to a standard format for transmission to the telephone switch. The power supply for the device is derived from the telephone network and the computer interface.

Abstract: A telephone receptacle for releasably affixing a portion of a telephone handset thereto. A retractable latch member latchingly engages with a corresponding, mated latching surface formed on the telephone handset when the latch member is positioned in the latch position. An actuation force applied to either the left-hand side portion, or the right-side portion of the telephone receptacle retracts the retractable latch member into a release position thereby permitting the telephone handset to be removed from the telephone receptacle.

Abstract: A test system directed to apparatus for transmitting and receiving multiple telephone transmission signals over a single twisted pair. The system converts an analog signal from a local switching station to an 80 ksymbols/sec signal for transmission over a twisted pair by a line card. A remote terminal converts the 80 ksymbols/sec signal back into a conventional analog signal for use in conventional telephone, facsimile or other related equipment. The test equipment separately tests the entire system, the line card portion of the system, the remote terminal portion of the system, and the twisted pair.

Abstract: A multi-purpose telephone accessory unit for persons who use a telephone for extended periods of time. It is connected to a conventional telephone by removing the telephone cord from the normal handset and plugging it into the accessory unit. The unit wears a headset equipped with two independently controlled ear piece receivers and a mouth piece transmitter. An external wall plug type A.C./D.C. transformer is used to provide power for the unit. The unit has separate volume controls and separate equalizers for the respective ear piece receivers. A mute switch is connected into the voice transmission circuit to allow the user to speak with other persons in their area without the person on the other end of the telephone line hearing the conversation. An internal microphone is also provided that can be connected through the mute switch that allows the user to pick up voices and sounds in their immediate vicinity of the unit without the user having to remove the ear receiver unit.

Abstract: An adaptor for connecting the conventional plug which connects a telephone handset to a modem so that a computer connected to the modem may be operably connected to the transmitter circuitry associated with any conventional dual tone multiple frequency (DTMF) telephone.

Abstract: A multipurpose headset amplifier for the connection of a headset (11) to a telephone instrument comprises a housing (5) having an ascending, thready holder (10) for a headset (11) and connection jacks (21, 22, 23) for the headset (11), the telephone instrument (22) and for the telephone instrument's handset, the housing having at the upper side comprises manuel operating members (6, 7, 8) for the adjustment of the device, and manual controls (15) at the underside for the adaptation of a headset to the impedance and signal level of any telephone instrument. The amplifier comprises an internal power supply (12) and a jack (13) for external power supply. The amplifier is furthermore provided with a microphone switch having a light-emitting diode (9), a volume control (7) and a switch (6).

Abstract: An apparatus for "hands off" control of a Voice Mail System over a telephone line by a user to allow the user to simultaneously perform other functions such as manually processing the "oral mail" to take notes, do data entry or the like. The apparatus includes a foot pedal that is wired with switches. The foot pedal switches are connected through an interface circuit to a DTMF tone generator or a generator of digital signals corresponding to VMS functions. The interconnection is such that depending upon the pedal activated a different tone or digital signal will be generated. The user can readily reconnect the interface to vary the signal to pedal correspondence for changes in Voice Mail Systems or to implement other Voice Mail System commands. The DTMF tone generator is connected in series between the hand set and base set of a telephone so that system can be readily connected to an existing telephone and so that the tones can be sent over the phone line to a Voice Mail System.

Abstract: An auto response phone system is provided that allows a user to automatically screen calls and respond without even talking into a telephone receiver. In one embodiment of the invention the system is built into a conventional telephone. In an alternative embodiment the system is built into a separate case and operates as an accessory. The system stores several messages in non-volatile electronic format. The user picks up the phone when called to identify the caller. The user can then speak to the caller or automatically send one of the pre-recorded messages. A special night button automatically gives a night time message and disables the telephone ringer. If the caller sends a predetermined sequence of touch tones the user's ringer is re-activated to permit emergency calls to be answered. A monitor capability allows the user to monitor all telephone transactions.

Abstract: A control and switching unit used with at least two devices for transmitting information or voice communication over telephone lines. The control and switching unit is provided with a series of relays to ensure that only one of the devices receives or transmits information at any one time. A timing circuit is utilized such that if one of the devices is a telephone, the second device would not be able to gain access to the telephone line if the telephone is ringing. Additionally, if the telephone is in use, the secondary device, such as a modem, could be selected and this secondary device would gain access to the telephone line after the use of the telephone has been discontinued.

Abstract: An interface arrangement (2) comprising interface circuits (5,7) and processor (14) allows a personal computer (10) to operate in conjunction with a telephone subset (1) associated with a main switch system (9) in which the signalling systems used by the telephone subset and the computer differ. The interface arrangement allows the subset and the computer to be connected to the subsets switching system to permit at least some of the subsets signalling functions to be performed by the computer.

Abstract: A data transmission processing machine interposed between a host computer and a telephone line comprises a telephone circuit, a modem, a keyboard, and a mode selection switch. Responsive to a mode selected by the mode selection switch, the keyboard is operated either as a dial for the telephone or as a data entry keyboard for the modem.

Abstract: Individual security subscriber line module including a generally rectangular, hollow box-like structure including a top, bottom, opposed sides and opposed first and second ends, such structure providing an internal space for receiving an individual circuit; a pair of subscriber wiring terminals mounted on the top for connection to a subscriber line, a plug connected to the pair of subscriber wiring terminals by first electrical conductors; a jack mounted on the top and provided with second electrical conductors for connecting the jack to the incoming telephone company line, the jack for having the plug plugged therein to interconnect the pair of subscriber wiring terminals and thereby the subscriber line to the incoming telephone company line and the plug for being unplugged from the jack to provide a demarcation point between the subscriber line and incoming telephone company line, and upon the plug being unplugged from the jack the jack for receiving the plug of an operating telephone to facilitate determin

Abstract: A telephone ringing adapter has a preset number of ringing tones of a calling signal applied from a telephone call diverting device or the like. When the incoming ringing number coincides with the preset number, a relay is energized so that the calling signal is applied to a conventional telephone answering device which is connected to the adapter to comprise a loop circuit and take a message from the calling party. After the hang-up of the calling party, the relay is released and it returns to standby mode for the next call. So, even when the final call diverted party doesn't answer the call, it is possible for a general telephone answering device to operate the automatic answering and recording function for the calling party after the preset number of calling signals.

Abstract: An amplifier in a housing for receiving and detecting the presence of portable paging devices that produce an audible signal when activated. The amplifier allows the connection of a large capacity annunciator or visual alarm. Circuitry is provided to connect the output of the amplifier to the bell of conventional telephone sets without affecting its normal operation. The telephone set bell can be activated with a voltage signal different from the one it normally generates so that a user can distinguish the two calls.

Abstract: A telephone device, typically a terminal, that receives a.c. communication signals and that sinks d.c. current to provide the off-hook signal is powered from (i) the telephone lines and, if line voltage is less than 7.4 v.d.c., from (ii) a 6 v.d.c. battery. Connection to telephone lines of voltage greater than 7.4 v.d.c. recharges the battery. The terminal further contains a CMOS microprocessor that may be declocked and placed in standby mode to conserve power. When so placed, the microprocessor maintains some of its signal lines at a logic High, 6 v.d.c., condition. In order to both unpower circuits such as a display, a memory, a DTMF dialer, and a modem to which the microprocessor signal lines connect, and to (ii) disrupt current leakage paths from the signal lines to ground through the unpowered circuits, the ground is removed from the circuits. This removal, controlled by a signal from the standby microprocessor, is performed by a transistor switch.

Abstract: A ground start key switch for use with a modular duplex adapter to permit momentarily shorting a pair of jack terminals includes a switch actuator mechanism adapted to be mounted onto the modular duplex adapter having a pair of jack terminals and a conductor member attached to the switch actuator mechanism. The switch actuator mechanism includes a resilient lever arm which is depressible for causing engagement of the conductor member with the pair of jack terminals so as to electrically short the pair of jack terminals together. When the resilient lever arm is released, the resiliency thereof returns the conductor member thereof to its normal position at which the conductor member is disengaged from the pair of jack terminals such that the latter are not longer shorted together.

Abstract: Telephone network interface apparatus including a base and a wall circumscribing the base and extending outwardly therefrom, the base and wall cooperatively providing an open compartment having a telephone company compartment portion and a subscriber compartment portion; the telephone company compartment portion is for having a plurality of pairs of telephone company terminals mounted therein for connection to a plurality of incoming telephone company lines and the subscriber compartment portion for having a plurality of subscriber terminals mounted therein for connection to a plurality of subscriber premises lines. A telephone company cover is included and is mounted pivotally to a portion of the wall and is for being closed and fastened over the telephone company compartment portion; first fastening means are included for fastening the telephone company cover closed over the telephone company compartment portion.

Abstract: Telephone network interface apparatus for interconnecting incoming telephone company wiring to subscriber premises wiring including a base including a bottom and an outwardly extending wall circumscribing the bottom, the wall includes opposed first and second wall portions and the bottom and wall provide a compartment divided generally into opposed first and second compartment portions, the first compartment portion is adjacent the first wall portion and the second compartment portion is adjacent the second wall portion, the first compartment portion is for having first terminals mounted therein for connection to the telephone company wiring and the second compartment is for having second terminals mounted therein for connection to the subscriber premises wiring; a telephone company cover mounted pivotally to the second wall portion and for overlying the entire compartment, the telephone company cover includes opposed first and second portions, the first portion is solid and is for overlying and closing the f

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

Abstract: A handset for telephones and the like has electro-acoustical capsules for hearing and speaking, mounted between an upper housing shell and a lower housing shell of the handset. Each of the capsules is connected to the handset cord by a pair of leads received in cutting clamp connections arranged on the rear sides of the hearing and speaking capsules, the opposed housing shells having projections pushing the leads into the cutting clamps. Preferably, the leads are mounted on a foil having openings for the cutting clamps and the projections, and also openings for guide pins, whereby the leads are guided into the cutting clamps when the upper and lower housing shells are brought together on the leads.

Abstract: An apparatus for connecting a telecommunications device, such as a computer or facsimile machine modem, to a telephone line via a telephone set. The telephone set includes a base and a handset connected to the base by a handset cord. The handset cord has at one end a handset plug and the base has a base jack for receiving the handset plug. The apparatus selectively electrically couples one of the handset and the telecommunications device to the base. The apparatus includes a first plug for electrically coupling with the base jack, a first jack for electrically coupling with the handset plug, and the second jack for electrically coupling with the telecommunications device connecting plug. A switch, manually selectable between a first position and a second position, electrically couples the first plug with the first jack when in the first position.

Abstract: An apparatus for remotely controlling electronic equipment such as a VTR using a remote telephone set. The electronic equipment has a timer reservation unit which causes the electronic equipment to start a predetermined operation at a predetermined time in accordance with externally inputted reservation information and to become inoperable after a predetermined period. The timer reservation unit includes an input unit, and a remote controller is coupled to the input unit of the timer reservation unit to perform wireless communication therebetween. The remote controller is constructed such that the reservation information is transmitted to the input unit of the timer reservation unit in response to a predetermined push button operation or dial operation of the remote telephone set.

Abstract: A system allowing selective connection of various types of external apparatuses to a telephone set, which system comprises a plurality of switching circuits connected to the external apparatuses and a plurality of external apparatus interface circuit having mutually different characteristics and connected through the plurality of switching circuits to the external apparatuses, wherein any one of these switching circuits is turned on and at the same time the other circuits are turned off to selectively connect one of the interface circuits to one of the external apparatuses.

Abstract: A telephone/facsimile system including a plurality of telephones and a facsimile device connected to a common telephone line wherein incoming calls are automatically switched from the telephone to the facsimile device as appropriate and the use of a common telephone line for the telephone and the facsimile device for both incoming and outgoing calls is transparent to users.

Abstract: A data station termination circuit for connecting a four-wire, voice frequency transmission facility to either a four-wire or two-wire subscriber station in a telephone communication system for effecting a four-wire or two-wire mode of operation includes a gain/loss network coupled to a receive-in port for receiving incoming voice frequency data signals from a first signal transmission path of the four-wire transmission facility and for amplifying or attenuating the incoming voice frequency data signals. The gain/loss network is formed of a single operational amplifier, a set of binary weighted resistors, and a plurality of single-pole, single-throw slide switches. Other features disclosed include a battery back-up for use during a loopback condition and an optional equalization network for use in a second signal transmission path.

Abstract: The invention relates to circuitry for providing and monitoring the status of telephones, especially those used in conjunction with advanced telephone answering machines, such as is also disclosed herein. The voltage on the extension line leading to the telephone set (termination device) is monitored to determine whether the telephone set is on-hook or off-hook. Also, a tone decoder monitors DTMF signals on the extension line. The telephone set, when off-hook, is normally connected to the subscriber line. However, if a predetermined digit is keyed into the telephone set, the telephone set will be disconnected from the subscriber telephone line and connected to a selectively actuable current source. The telephone set, being powered by the current source and being disconnected from the subscriber line, can then be used for the control and monitoring of the telephone answering machine. Also, the current source is protected against the application of the subscriber line voltage.