DEVICE FOR TELEPHONE LINE DISENGAGEMENT FOLLOWING THE RECEPTION OF A CALL WAITING

Abstract: A device for telephone line disengagement following the reception of a call-waiting signal, comprising means adapted to detect electrical variations of the telephone line consequent to the transmission of a call-waiting signal, the electrical variation detection means being connected to means for disengaging the line which are adapted to disengage the modem from the telephone line, allowing the user to reply to the incoming call.

Description: DEVICE FOR TELEPHONE LINE DISENGAGEMENT FOLLOWING THE RECEPTION OF A CALL-WAITING TECHNICAL FIELD The present invention relates to a device for telephone line disengagement following the reception of a call-waiting signal. More particularly, the invention relates to a device for telephone line disengagement which allows to disengage the line when a call-waiting signal arrives in order to allow the user to reply to such call. BACKGROUND ART As is known, the increasing growth and the corresponding diffusion of the Internet has brought many users to connect daily to it for considerable time, thus keeping the home telephone line engaged. Since connection to the Internet lasts on average for considerable time, because of the fact that the user, once connected, loses perception of time and "surfs" for considerable time, incoming telephone calls to the user's number cannot be detected by the user, because the line is engaged and is therefore found busy. However, it is evident that in some situations it is indispensable to receive calls which can be of extreme interest, and in this case the user does not have this possibility. Modern telephone exchanges send a call-waiting signal which allows the user, even if he is busy with other calls, to be aware that another subscriber is calling him and therefore to decide whether he wishes to continue the conversation currently in progress or answer the incoming call. However, connection to the Internet occurs by means of a device, commonly known as modem, which allows to connect the user's personal computer to the network by means of the telephone system and the server that allows access to the network and accordingly allows to send and receive data from the network. However, the modem is "silent" with respect to call-waiting signals sent by the exchange. Substantially, a call-waiting signal is generally ignored by the modem and therefore the user cannot be aware of the incoming call. SUMMARY OF THE INVENTION The aim of the present invention is to provide a device for telephone line disengagement following the reception of a call-waiting signal which allows the user to disengage the line and answer the incoming call. Within this aim, an object of the present invention is to provide a device for telephone line disengagement following the reception of a call-waiting signal which allows the user to decide whether to set himself in the condition for receiving a call or to completely bar any incoming calls. Another object of the present invention is to provide a telephone line disengagement device which can be connected to any kind of modem employed by the user. Another object of the present invention is to provide a telephone line disengagement device which can be applied externally with respect to the modem or can be directly internal to the apparatus meant to be connected to the modem. Another object of the present invention is to provide a device for telephone line disengagement following the reception of a call-waiting signal which is highly reliable, relatively simple to manufacture and at competitive costs. This aim and these and other objects which will become better apparent hereinafter are achieved by a device for telephone line disengagement following the reception of a call-waiting signal, characterized in that it comprises means adapted to detect electrical variations of the telephone line consequent to the transmission of a call-waiting signal, said electrical variation detection means being connected to means for disengaging the line which are adapted to disengage the modem from the telephone line, allowing the user to reply to the incoming call. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the invention will become better apparent from the description of preferred but not exclusive embodiments of the device according to the present invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a block diagram of the connection of a device according to the present invention to the telephone system and to the modem of the user; Figure 2 is a block diagram of the circuit that constitutes the device according to the present invention; Figure 2a is a view of a second embodiment of the circuit according to the invention; and Figure 3 is a detailed block diagram of the connection of the device according to the present invention. WAYS OF CARRYING OUT THE INVENTION With reference to the figures, in which identical reference numerals designate identical elements, the device according to the present invention, generally designated by the reference numeral 1, is meant to be connected between the telephone system 2, in which 2a and 2b designate the wires that constitute the wire pair of the telephone line, and a modem 3, which is in turn connected to a personal computer 4, as shown in Figure 1. Figure 2 is a block diagram of the circuit of the device according to the present invention, which comprises means 5 for the input of the telephone line which are adapted to allow connection between the device 1 and the telephone line 2; said means are connected to rectifier means 6, an output of which is connected to means 7 for actuating the signals and disengaging the telephone line, which comprise for example relays. Means 8 adapted to generate a useful signal are conveniently connected between the rectifier means 6 and output means 9 which are adapted to allow the connection of the device 1 to the modem 3. The means 8 are conveniently constituted for example by at least one resistor, whose terminals are connected to means 10 for acquiring the signal that is present on the resistor; said means are conveniently constituted for example by at least one operational amplifier. The output of the operational amplifier constitutes a first input of logic means 11, which are conveniently constituted for example by an AND gate, a second input whereof is constituted by the output of switching means 12 which are adapted to be actuated by the user in order to pass from a position a, in which the device according to the invention is deactivated, to a position b, in which the device is standing by for a call-waiting signal, as described in detail hereinafter. Conveniently, the switching means 12 drive at least one signaling LED 13 which is adapted to indicate the status of the device. Likewise, the means 7 drive at least one LED 14 and at least one buzzer 15. Figure 3 illustrates in detail the connection of the device 1 according to the invention, by virtue of the input means 5, to the telephone system, and particularly to the wire pair 2a, 2b. The output of the device according to the invention, constituted by the output means 9, allows connection, by means of a connecting cable 16, to the modem 3, which is in turn connected to the personal computer 4, as shown in Figure 1. With reference to the figures, the operation of the device according to the present invention is as follows. For connection to the Internet, the user uses the modem 3; the modem, controlled by the computer 4, activates a data link-up to the server that operates the service. The electronic hardware (i.e., the modem and the server) interconnects, performing handshaking methods which are required in order to perform data transmission and ensure the standard to be complied with throughout the connection period. For mutual comprehension, these devices perform an exchange of parameters known as "protocol negotiation". Once this preliminary step has ended, the modem 3 sends over the carrier the information required for online activity. The carrier is therefore always present throughout the period during which the user is online with the computer network. When the call-waiting signal arrives, the modem 3 performs the same initial procedures, i.e. protocol negotiation, and the device according to the invention intervenes at this point, since during this step the modem 3 stops sending the carrier. The absence of the carrier therefore becomes a useful element for the intervention of the device 1, which was standing by for the event. Substantially, the telephone exchange, in transmitting the call-waiting signal (audio signal), changes the electrical values, influencing the communication established between the modem 3 of the user and the server. The variation in these values forces the modem 3 and the server to renegotiate the parameters of the protocol, consequently interrupting the carrier. When the modem 3 engages the telephone line, the current initially has the following path: from the terminal 2a of the input means 5 it passes to the rectifier means 6, to the resistor 8, and to the contact c of the output means 9, then it enters the modem 3, exits again on the contact d of the output means 9, and passes to the contact 2b of the input means 5. In this manner, the current flows from the rectifier means 6, and if the contact of the switching means 12 is switched to the position a (idle position), the actuation means 7 for signaling and line disengagement keep the circuit closed on the modem. The means 7 further provide the necessary power supplies to the operational amplifier 10 and to the logic gate means 11. The operational amplifier 10 acquires the signals at the terminals of the resistor 8 and converts them into DC levels (polarity), The logic means 11 receive in input the polarities from the operational amplifier 10 and from the contact b of the switching means 12; when they match, because a call- waiting signal is in progress, the logic means 11 actuate the means 7 in order to open the power supply circuit that arrives from the rectifier means 6, thus interrupting the flow of current, and the modem 3 is automatically isolated. During this step, the switching means 12 must be switched to the contact b. Substantially, if the switching means 12 are in the position a, all the changes of status that arrive from the operational amplifier 10 and are due to the initial step (connection of the modem 3 to the server, with touch-tone digit dialing signal and exchange of protocol-related frequencies) have no effect on the output of the logic means 11, since there is no enable signal originating from the switching of the switching means 12 on the contact b. The position a of the switching means 12 (idle position) must be maintained by the user during the preliminary steps and also thereafter unless he wishes to activate automatic telephone line disengagement. When the user is online, by shifting the switching means 12 to the contact b, the device remains in standby for the event, i.e., for the call- waiting signal. Upon arrival of the call-waiting signal, when the parameters are renegotiated, the operational amplifier 10, together with the contact b, form the clearance signal for the output of the logic means 11, which send the command to the means 7 in order to disengage the line. The actuation means 7 for line signaling and disengagement conveniently comprise mechanical and optoelectronic relays, switching transistors, SCRs, et cetera, whose contacts open or close the circuit at the terminals of the output of the rectifier means 6. The actuation means 7 operate in the initial step (when the modem 3 engages the line), with the position of the switching means 12 on the contact b, and store this state. When the switching means 12 are shifted to b (for event standby), they still allow the flow of current in the modem 3, supplying power to the circuits of the device 1, which is operational and is standing by for the event. The means 7 further supply the optional circuits 14 and 15 of the optical and acoustic signaling devices that are activated instead of automatic disengagement. Conveniently, the rectifier means 6 are constituted for example by diodes connected in a Graetz-bridge configuration, in order to always ensure the same polarity of the power supply to the circuits of the device, making it independent with respect to the input contacts 2a and 2b of the input means 5. A visual indicator 17 indicates that the modem 3 has engaged the telephone line and that accordingly the device is powered. The user, as mentioned, must then act on the switching means 12 and while he is online he can decide to suspend automatic disengagement, by returning the switching means into the position a, and at any time he can then return the switching means 12 to the position b for standing by for the call-waiting signal. The LED 13 indicates that the device 1 is active and can disengage the line following the call-waiting signal. The lighting of the LED 13 is determined by the position b of the switching means 12. The device according to the invention can be configured as a unit which is external to the modem or can be installed directly inside the modem, the personal computer, or any other device that has to engage the telephone line for its operation. The device can further be powered with a battery or accumulator or with a built-in or external power supply, or it can be self-powered by the telephone line. In practice it has been observed that the device according to the invention fully achieves the intended aim and objects, since it allows to automatically disengage the telephone line when a call-waiting signal arrives, thus allowing the user to reply to the call, interrupting his online session on the Internet. The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept. Thus, for example, the operational amplifier 10 can be replaced by a conventional amplifier which receives in input the same signals acquired at the terminals of the resistor 8; said signals, at the output of the amplifier, are separated from the DC component, are then rectified and are finally sent to a filtering cell, thus achieving the same result obtained by using the operational amplifier 10 shown in Figure 2. Moreover, an additional variation can be provided by the replacement of the means for detecting the electrical variations of the line, constituted by the operational amplifier 10 and by the resistor 8, with a transistor 20 which is connected, by means of its base terminal, to the rectifier 6 by interposing a first capacitor 21, and to the logic means 11. A second capacitor 22 is connected between the emitter terminal of the transistor 20 and the positive of the power supply, while the collector terminal of the transistor 20 is connected to the negative (ground) of the power supply voltage across a first resistor 23. A second resistor 24 is instead connected between the base terminal and the collector terminal of the transistor 20. In this manner, the transistor 20 acts as an amplifier for detecting changes of state and as a generator of the logic level for driving the logic means 11. The transistor works in the off mode when the carrier is present; when said carrier ceases, with the effect of renegotiation, it switches on, charging the capacitor 22 for the logic level. An additional variation is provided by the fact that the circuit according to the invention can analyze, instead of the absence of the carrier, the renegotiation frequencies (which are generally very strong) exchanged between the modem and the servers, thus always monitoring electrical variations of the line which are not linked, however, to the presence or the absence of the carrier. All the details may furthermore be replaced with other technically equivalent elements.

Claims: CLAIMS 1. A device for telephone line disengagement following the reception of a call-waiting signal, characterized in that it comprises means adapted to detect electrical variations of the telephone line consequent to the transmission of a call-waiting signal, said electrical variation detection means being connected to means for disengaging the line which are adapted to disengage the modem from the telephone line, allowing the user to reply to the incoming call. 2. The device according to claim 1, characterized in that said means for detecting the electrical variations of the line are adapted to detect the absence of a carrier between said modem and the server to which the modem connects for link-up to a computer network. 3. The device according to claim 1, characterized in that said means for detecting the electrical variations of the line are adapted to detect protocol negotiation signals sent by said modem to said server over said line. 4. The device according to one or more of the preceding claims, characterized in that said means for detecting the electrical variations of the line comprise at least one operational amplifier which is adapted to detect a useful signal which is present at the terminals of at least one resistor which is cascade-connected to rectifier means which are connected to input means, which are in turn meant to be connected to said telephone line. 5. The device according to one or more of claims 1 to 3, characterized in that said means for detecting the electrical variations of the telephone line comprise at least one transistor which is connected between said rectifier means and said logic means, a first capacitor being connected between the base terminal of said transistor and said rectifier means, a second capacitor being connected between the emitter terminal of said transistor and a power supply voltage, a first resistor being connected between the collector terminal of said transistor and the ground, a second resistor being connected between the base terminal and the collector terminal and said transistor. 6. The device according to one or more of the preceding claims, characterized in that it comprises switching means which are adapted to switch between an inactive position of said device and a position for preparing for the disengagement of said telephone line. 7. The device according to one or more of the preceding claims, characterized in that it comprises logic means which receive in input the output of said at least one operational amplifier and the output of said switching means, in order to drive said actuation means. 8. The device according to one or more of the preceding claims, characterized in that said at least one resistor is connected between said rectifier means and said output means which allow connection to said modem. 9. The device according to one or more of the preceding claims, characterized in that it comprises at least one signaling LED which is driven by said switching means. 10. The device according to one or more of the preceding claims, characterized in that it comprises at least one signaling LED which is driven by said rectifier means. 11. The device according to one or more of the preceding claims, characterized in that it comprises at least one signaling LED and at least one buzzer, both of which are driven by said actuation means. 12. The device according to one or more of the preceding claims, characterized in that it is connected between said telephone line and said modem. 13. The device according to one or more of the preceding claims, characterized in that it is configured as a unit which is external to said modem. 14. The device according to one or more of the preceding claims, characterized in that it is accommodated in any apparatus adapted to engage said telephone line. 15. The device according to one or more of the preceding claims, characterized in that said logic means comprise an AND gate, a first input whereof is constituted by the output of said at least one operational amplifier and whose second input is constituted by the output of said switching means. 16. The device according to one or more of the preceding claims, characterized in that it is self-powered by the telephone line. 17. The device according to one or more of the preceding claims, characterized in that it is powered by means of an internal battery. 18. The device according to one or more of the preceding claims, characterized in that it is powered by means of the electrical mains. 19. A method for disengaging the telephone line following the reception of a call-waiting signal, characterized in that it comprises the steps of: following the reception of an incoming telephone call-waiting signal on a telephone line engaged by a connection of an auxiliary apparatus, detecting electrical variations undergone by said telephone line; driving means for actuating the disengagement of said telephone line on the part of said auxiliary apparatus in order to allow to reply to said telephone call. 20. The method according to claim 19, characterized in that said electrical variations of the telephone line are due to the absence of the carrier on which the data for the connection of said auxiliary apparatus to said telephone line are sent. 21. The method according to claim 19, characterized in that said electrical variations of said telephone line are due to the renegotiation of the connection protocol of said auxiliary apparatus.

Inventors: FALACE LUCIO, TORTORA GIUSEPPE, TORTORA ROSARIO, FALACE, LUCIO, TORTORA, GIUSEPPE, TORTORA, ROSARIO
Applicants: FALACE LUCIO, TORTORA GIUSEPPE, TORTORA ROSARIO, FALACE, LUCIO, TORTORA, GIUSEPPE, TORTORA, ROSARIO
Application year: 2000
Main classification: H04M3
IPC codes: H04M3, H04M7