Abstract:
Conventional modems coupled in parallel to a coupling need a sharing apparatus, which can be avoided by providing each modem with a detector for detecting upstream/downstream signals to be transceived by other modems coupled in parallel. The detector has a distinguisher for distinguishing upstream signals and downstream signals. An additional filter between the coupling and detector prevents the modem from interfering with the other modems coupled in parallel. The modem may have an active/passive state corresponding with a lower/higher impedance.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a modem to be coupled to a network via a coupling and comprising a detector for detecting coupling signals. 
   Such a modem is generally known, with the network, for example, being a public and/or private telecommunication network, and with the coupling being, for example, a wired connection or a wireless coupling. The detector detects the signals flowing via the coupling, e.g., ringing signals indicating that a call is made from the network to the modem and/or DC currents indicating that a telephony device is connected in parallel to the modem is involved in a call. 
   U.S. Pat. No. 5,530,951 discloses a telephone line sharing apparatus for enabling a plurality of telecommunications devices of any type to share a plurality of single subscriber telephone lines. 
   The known modem is disadvantageous, inter alia, due to several of these modems when connected in parallel, especially but not exclusively Digital Subscriber Line modems or DSL modems, needing such a complicated sharing apparatus. 
   SUMMARY OF THE INVENTION 
   It is an aspect of the invention, inter alia, of providing a modem which can be connected in parallel to an other modem without needing the complicated sharing apparatus. 
   The modem according to the invention is characterized in that the modem comprises a transceiver for transceiving upstream/downstream signals via the coupling, with the detector detecting upstream/downstream signals to be transceived by an other modem coupled to the coupling in parallel to the modem. 
   By providing the modem according to the invention with the detector for detecting upstream/downstream signals to be transceived by the other modem coupled to the coupling in parallel to the modem according to the invention, with each modem, of course, comprising the transceiver for transceiving upstream/downstream signals via the coupling, the modem according to the invention has knowledge of what is going on via the coupling at any time. 
   The invention is based on the insight, inter alia, that functions, such as processor capacity at a central location, can be relocated at decentralized locations, and vice versa, with especially, but not exclusively, Digital Subscriber Line modems or DSL modems already being provided with high processor capacities. 
   The invention solves the problem, inter alia, of providing a modem which can be connected in parallel to an other modem without needing the complicated sharing apparatus, by letting the modem according to the invention detect upstream/downstream signals to be transceived by an other modem coupled to the coupling in parallel to the modem according to the invention. 
   Upstream/downstream signals comprise upstream signals (for example, at 150 kHz) and/or downstream signals (for example, at 500 kHz). And, of course, more than two modems can be connected in parallel. 
   A first embodiment of the modem according to the invention is characterized in that the detector comprises a distinguisher for distinguishing upstream signals to be tranceived from the other modem via the coupling to the network and downstream signals to be transceived from the network via the coupling to the other modem. 
   By providing the detector in the modem according to the invention with the distinguisher for distinguishing upstream signals and downstream signals, the modem according to the invention has all knowledge of what is going on via the coupling at any time. 
   The distinguisher, for example, comprises two bandpass filters, one for the upstream and one for the downstream. 
   A second embodiment of the modem according to the invention is characterized in that the modem comprises a filter to be coupled to the coupling. 
   By providing the modem according to the invention with the filter, e.g., a highpass filter, during detecting, the modem according to the invention does not interfere with the other (possibly transceiving) modem. 
   A third embodiment of the modem according to the invention is characterized in that the modem comprises a switch coupled to the detector and to the transceiver for, in response to the detecting, switching the modem in an active/passive state. 
   By providing the modem according to the invention with the switch for switching the modem in an active/passive state, during detecting the modem will be in a passive state, and in case of no detection of present streams, the modem can be switched into an active state. 
   A fourth embodiment of the modem according to the invention is characterized in that the modem in the active/passive state corresponds with a lower/higher impedance. 
   Then, an active state will correspond with the coupling (as well as the other modem) noticing a lower impedance, and a passive state will correspond with the coupling (as well as the other modem) noticing a higher impedance. 
   A fifth embodiment of the modem according to the invention is characterized in that the modem comprises a hybrid comprising a first serial circuit including a first impedance and a first switch with a first point of them to be coupled to a first wire of the coupling, and comprising a second serial circuit including a second impedance and a second switch with a first point of them to be coupled to a second wire of the coupling, and comprising a third serial circuit including third impedances located between the wires of the coupling and coupled to the first points of the first and second serial circuits, and comprising a fourth serial circuit including fourth impedances coupled to second points of the first and second serial circuits. 
   Such a hybrid, with the switches being in a conductive state, corresponds with a lower impedance (active state), and with the switches being in a non-conductive state, corresponds with a higher impedance (passive state), whereby the detector is to be coupled to common points of the third and fourth serial circuits, and with the rest of the modem to be coupled to the second points. 
   The invention further relates to a method for coupling a modem to a network via a coupling and comprising a step of detecting coupling signals. 
   The method according to the invention is characterized in that the method comprises a step of detecting upstream/downstream signals via the coupling to be transceived by an other modem coupled to the coupling in parallel to the modem. 
   A first embodiment of the method according to the invention is characterized in that the method comprises a step of distinguishing upstream signals to be tranceived from the other modem via the coupling to the network and downstream signals to be transceived from the network via the coupling to the other modem. 
   A second embodiment of the method according to the invention is characterized in that the method comprises a step of filtering between the modem and the coupling. 
   A third embodiment of the method according to the invention is characterized in that the method comprises a step of, in response to the detecting, switching the modem in an active/passive state. 
   U.S. Pat. No. 5,530,951 discloses a telephone line sharing apparatus for enabling a plurality of telecommunications devices of any type to share a plurality of single subscriber telephone lines. U.S. Pat. No. 6,259,775 discloses a multi-line modem interface circuit including a sensing circuit for identifying a status of one or more external lines. This interface circuit is operable to automatically monitor a line to determine if it&#39;s ringing, determine whether it&#39;s allowed and couple the line to the modem for potential answer. U.S. Pat. No. 6,092,122 discloses a Digital Subscriber Line modem or DSL modem. None of these references discloses the modem according to the invention. All these references, including further references cited with respect to these references, are considered to be included in this patent application. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be further explained in more detail as shown in the drawings, whereby: 
       FIG. 1  discloses a first modem according to the invention comprising a detector and a tranceiver and a highpass filter, and 
       FIG. 2  discloses a second modem according to the invention comprising a detector and a transceiver and a hybrid. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  discloses a first modem  1  according to the invention (for example, a Digital Subscriber Line modem or DSL modem) comprising a processor  10  and a transceiver  11  coupled via a connection  26  to, for example, a PC (not shown) and via a connection  25  to a switch  16 , which via a connection  22  is coupled to a highpass filter  17  and to bandpass filters  14  and  15 . Bandpass filters  14 ,  15  are coupled via connections  23 ,  24  to detectors  12 ,  13 . Highpass filter  17  is coupled via a connection  21  to a switch  18 , which is coupled via a (wired or wireless) coupling  20  to a (public and/or private) network (not shown) and is coupled wiredly or wirelessly to an other modem (not shown). Processor  10  is coupled via control connections to switches  16 ,  18 , to detectors  12 ,  13  and to transceiver  11 . 
   The first modem  1  according to the invention comprises detectors  12 ,  13 , transceiver  11  and highpass filter  17  functions as follows. 
   According to a first embodiment, the other modem (not shown) is not involved in any communication with the network (not shown) (in other words being in a passive state), and the PC (not shown) wishes to start a communication with the network. Then, processor  10  is informed, which switches switch  18  into a conductive state and which controls detectors  12 ,  13  for starting detecting, with detector  12 , for example, detecting upstream signals (at, for example, 150 kHz and filtered by bandpass filter  14 ) flowing from the other modem to the network and with detector  13 , for example, detecting downstream signals (at, for example, 500 kHz and filtered by bandpass filter  15 ) flowing from the network to the other modem. Due to the other modem not being in an active state, detectors  12 ,  13  will not detect any streams exchanged between the other modem and the network, and inform processor  10 . In response to this, processor  10  informs the PC to start generating data and switches switch  16  into a conductive state and controls transceiver  11  such that the data, together with set-up-information, is sent to the network and that further data originating from the network can be processed. 
   According to a second embodiment, the other modem (not shown) is involved in a communication with the network (not shown) (in other words being in an active state), and the PC (not shown) wishes to start a communication with the network. Then, processor  10  is informed, which switches switch  18  into a conductive state and which controls detectors  12 ,  13  for starting detecting, with detector  12 , for example, detecting upstream signals at, for example, 150 kHz and filtered by bandpass filter  14 ) flowing from the other modem to the network and with detector  13 , for example, detecting downstream signals (at, for example, 500 kHz and filtered by bandpass filter  15 ) flowing from the network to the other modem. Due to the other modem now being in an active state, detectors  12 ,  13  will detect streams exchanged between the other modem and the network, and inform processor  10 . In response to this, processor  10  informs the PC that communication is now impossible and keeps switch  16  in a non-conductive state. 
   According to a first possibility, the PC must take the initiative of trying again to start a communication with the network. Then, processor  10  will bring switch  18  into a non-conductive state, for example. 
   According to a second possibility, the processor  10 , via detectors  12 ,  13  keeps on monitoring coupling  20 , and keeps switch  18  in the conductive state, for example. As soon as the other modem has finished its communication, processor  10  brings switch  16  into a conductive state, informs the PC and the transceiver, etc. 
   According to a third embodiment, the PC knows that the network could start a communication with the PC via modem  1 , and informs processor  10  which brings switch  18  into a conductive state (or keeps it in a conductive state) and monitors coupling  20  via detector  13 , or the processor  10  knows that the network could start a communication with the PC via modem  1 , and informs the PC and brings switch  18  into a conductive state (or keeps it in a conductive state) and monitors coupling  20  via detector  13  etc. 
   In  FIG. 1 , detectors  12  and  13  and bandpass filters  14  and  15  may, partly or entirely, be located, alternatively or additionally, for example, inside transceiver  11  and/or for example, in parallel to high pass filter  17  and/or switch  18 . 
     FIG. 2  discloses a second modem  3  according to the invention (for example, a Digital Subscriber Line modem or DSL modem) comprising a processor  30  and a transceiver  31  coupled via a connection  58  to, for example, a PC (not shown) and via a connection  55  to a second point of a first serial circuit including a first impedance  37  and a first switch  34  with a first point of them to be coupled to a first wire  50  of the coupling  50 ,  51  and via a connection  57  to a second point of a second serial circuit including a second impedance  38  and a second switch  35  with a first point of them to be coupled to a second wire  51  of the coupling  50 ,  51 . A third serial circuit including third impedances  39 ,  40  located between the wires  50 ,  51  of the coupling  50 ,  51  is coupled to the first points of the first and second serial circuits, and a fourth serial circuit including fourth impedances  32 ,  33  is coupled to the second points of the first and second serial circuits. A detector  36  is located between common points  52 ,  56  of the third and fourth serial circuits. Again (wired or wireless) coupling  50 ,  51  is coupled to a (public and/or private) network (not shown) and is coupled wiredly or wirelessly to another modem (not shown). Processor  30  is coupled via control connections to switches  34 ,  35 , to detector  36  and to transceiver  31 . 
   The second modem  3  according to the invention comprising detector  36 , transceiver  31  and hybrid  32 ,  33 ,  34 ,  35 ,  37 ,  38 ,  39 ,  40  functions as follows. 
   According to a fourth embodiment, the other modem (not shown) is not involved in any communication with the network (not shown) (in other words being in a passive state), and the PC (not shown) wishes to start a communication with the network. Then, processor  30  is informed, which controls detector  36  for starting detecting, with detector  36 , for example, detecting upstream signals (at, for example, 150 kHz) flowing from the other modem to the network and, for example, detecting downstream signals (at, for example, 500 kHz) flowing from the network to the other modem. Due to the other modem not being in an active state, detector  36  will not detect any streams exchanged between the other modem and the network, and inform processor  30 . In response to this, processor  30  informs the PC to start generating data and brings switches  34 ,  35  into a conductive state and controls transceiver  31  such that the data, together with set-up-information, is sent to the network and that further data originating from the network can be processed. 
   According to a fifth embodiment, the other modem (not shown) is involved in a communication with the network (not shown) (in other words being in an active state), and the PC (not shown) wishes to start a communication with the network. Then, processor  30  is informed, which controls detector  36  for starting detecting, with detector  36 , for example, detecting upstream signals (at, for example, 150 kHz) flowing from the other modem to the network and, for example, detecting downstream signals (at, for example, 500 kHz) flowing from the network to the other modem. Due to the other modem now being in an active state, detector  36  will detect streams exchanged between the other modem and the network, and inform processor  30 . In response to this, processor  30  informs the PC that communication is now impossible and keeps switches  34 ,  35  in a non-conductive state. 
   According to a first possibility, the PC must take the initiative of trying again to start a communication with the network. 
   According to a second possibility, the processor  30 , via detector  36  keeps on monitoring coupling  50 ,  51 . As soon as the other modem has finished its communication, processor  30  brings switches  34 ,  35  into a conductive state, informs the PC and the transceiver, etc. 
   According to a sixth embodiment, the PC knows that the network could start a communication with the PC via modem  3 , and informs processor  30  which monitors coupling  50 ,  51  via detector  36 , or the processor  30  knows that the network could start a communication with the PC via modem  3 , and informs the PC and monitors coupling  50 ,  51  via detector  36  etc. 
   According to a seventh embodiment, second modem  3  in  FIG. 2 , entirely or partly and, for example, excluding processor  30 , may correspond with transceiver  11  in  FIG. 1 , entirely or partly. 
   Each embodiment and/or each possibility can be combined with each other embodiment and/or each other possibility. Each part of each modem shown in the form of a block or (not shown), can be 100% hardware, 100% software or a mixture of both. Therefore, a detector also comprises a detecting function, a distinguisher also comprises a distinguishing function, a filter also comprises a filtering function, a switch also comprises a switching function, a transceiver also comprises a transceiving function etc. Each block shown or not shown can be integrated with each other block shown and/or not shown (for example, detector  12  and bandpass filter  14 , and/or detector  13  and bandpass filter  15 , and/or all four of them). Each processor will comprise a memory (not shown), and in addition, each block can have a further memory, which is not shown for efficiency purposes. 
   Each detector can comprise, for example, a demodulator and/or a comparator (or have a demodulating and/or a comparing function), thereby receiving comparison values from, for example, the processor. Each switch can, for example, be a relay, a transistor etc. Each impedance can, for example, be a resistance or an electronic impedance to be controlled by a processor, thereby possibly making switches superfluous. The values of the impedances of the hybrid, as well as the frequency values of the filters can be chosen voluntarily, with each choice having consequences known/clear to a person skilled in the art. Each transceiver can be divided into a separate transmitter and receiver, whereby in combination with the hybrid such a receiver possibly (and dependently upon the chosen values) either is located in parallel with the transmitter or with the detector (and then possibly combined with the detector). Further parts like further impedances can be added, for example, in connections  55 ,  57 , thereby causing consequences known/clear to a person skilled in the art.