Abstract:
An interconnection monitoring system for use with a multiple node wired network, the system comprising a plurality of transmitters, each located at a node of the network for transmitting a transmission from the node and a plurality of receivers, each located at a node of the network, for receiving a transmission at the node, the plurality of transmitters being operative to transmit along the network a signal bearing an identification code identifying the node from which a transmission takes place, the plurality of receivers being operative to receive transmissions from a plurality of nodes, bearing the identification codes and thus indicating the interconnection status of the nodes.

Description:
FIELD OF THE INVENTION 
     The present invention relates to devices for monitoring telecommunications systems. 
     BACKGROUND OF THE INVENTION 
     Conventional telephone networks include a multiplicity of interconnection nodes appearing at multiple levels deployed at various locations. FIG. 1 illustrates a typical conventional telephone network. 
     The network of FIG. 1 includes 10,000 telephone lines. A regional telephone exchange 10 is associated with a main distribution frame (MDF) 11 including, for example, 10,000 input connections 12, here designated as &#34;level A&#34; and 20,000 output connections 13, which define a second level, termed herein &#34;level B&#34;. 
     The main distribution frame output is connected via a plurality of multi-pair cables 14 to a plurality of cross-connection (CC) cabinets 20, typically 50 in number, each having, for example, 400 input pairs 21 which define a third level which is termed herein &#34;level C&#34;. The cross-connection cabinets have a multiplicity of output pairs 22, typically 600 in number, which define a fourth level termed herein &#34;level D&#34;. 
     Each cross-connection cabinet services a plurality of distribution boxes 30. Typically ten distribution boxes are provided for each cross-connection cabinet, each distribution box typically having sixty input pairs 32 which define a fifth level termed herein &#34;level E&#34;. The subscriber side, also known as the output side, of the distribution box typically has 120 output pairs 34, which define a sixth level which is termed herein &#34;level F&#34;. 
     The telephone network of FIG. 1 defines a multiplicity of nodes on the various levels described above. The nodes include: 
     a. Level A nodes which are at the input pairs 12 of the main distribution frame (MDF) 11. Each Level A node comprises a physical connection point at which a telephone line coming from an exchange 10 is connected to the input side of the MDF 11. 
     b. Level B nodes which are at the output pairs 13 of the MDF 11. Each Level B node comprises a physical connection point at which the output side of the MDF 11 connects to an MDF end of an individual pair within a multi-pair cable 14. Multi-pair cable 14 typically comprises 2000 cable pairs connecting an MDF to a plurality of cross-connection cabinets dispersed throughout the area served by the MDF. Therefore, each cable pair has an MDF end and a cross-connection cabinet end. 
     c. Level C nodes which are at the input pairs 21 of the cross-connection (CC) cabinets 20. Each Level C node comprises a physical connection point at which the cross-connection cabinet end of an individual cable pair within multi-pair cable 14 is connected to an individual input pair 21 of an individual cross-connection cabinet 20. 
     d. Level D nodes which are at the output pairs 22 of the cross-connection cabinets 20. Each Level D node comprises a physical connection point at which an output pair 22 of an individual cross-connection cabinet 20 connects to an individual cable pair within a multi-pair cable 24. Each multi-pair cable 24 typically comprises 100-200 cable pairs which connect an individual cross-connection cabinet output pair to an individual input pair of a distribution box 30. Therefore, each cable pair within multi-pair cable 24 has a cross-connection cabinet end and a distribution box end. 
     e. Level E nodes which are at the input pairs 32 of the distribution boxes (DB) 30. Each Level E node comprises a physical connection point at which the distribution box end of an individual cable pair within multi-pair cable 24 connects to an individual input pair 32 of an individual distribution box 30. 
     f. Level F nodes which are at the output pairs 34 of the distribution boxes 30. Each Level F node comprises a physical connection point at which an individual output pair 34 of an individual distribution box 30 is connected to a cable pair which forms part of a drop cable 35 corresponding to an individual subscriber line. 
     Reference is now made to FIG. 2 which is a pictorial illustration of a prior art individual cross-connection frame. A &#34;cross-connection frame&#34; is a general term referring to a CC or MDF or DB. Generally speaking, the term &#34;cross-connection frame&#34; refers to the physical location at which input pairs coupled to an upstream, higher level, cross-connection frame or exchange are selectably connected to output pairs coupled to a downstream, lower level, cross-connection frame or to a subscriber line. 
     Each cross-connection frame preferably is connected to: 
     a. at least one cable 100 which includes a first multiplicity of incoming cable pairs, connecting the cross-connection frame to a higher-level cross-connection frame or an exchange; and 
     b. at least one cable 105, which includes a second multiplicity of outgoing cable pairs connecting the cross-connection frame to a plurality of lower-level cross-connection frames or subscriber lines. 
     Each cross-connection frame preferably includes: 
     a. an input connection block array 110 including a first multiplicity of input blocks 120 typically corresponding in number to the maximum anticipated number of incoming cable pairs in cable 100 and being respectively permanently connected thereto; 
     b. an output connection block array 130 including a second multiplicity of output blocks 140 which typically exceeds the number of input blocks 120. The output blocks 140 typically correspond in number to the maximum anticipated number of outgoing cable pairs in cable 105 and are respectively permanently connected thereto; and 
     e. a plurality of jumper cable pairs 160, each of which selectably interconnects a pair of contacts within an individual input block 120 to a pair of contacts within an individual output block 140. 
     Each of jumper cable pairs 160 thus interconnects an input cable pair forming part of cable 100 with an output cable pair forming part of cable 105. 
     FIG. 3 illustrates parts of a conventional input block 120 and of a conventional output block 140 which are interconnected by a jumper cable. The input block 120 and the output block 140 each typically includes a plurality of pairs of conventional contact sets, such as 10 pairs of insulation displacement contact sets. 
     For simplicity, only one contact set 320 is shown in input block 120 and one contact set 321 is shown in output block 140. Each of contact sets 320 and 321 includes a plurality of conventional interconnected contacts 330 and 331 respectively, such as 2, 3 or 4 interconnected contacts. In FIG. 3, for example, there are shown two interconnected contacts 330 per contact set in the input block 120 and three interconnected contacts 331 per contact set in the output block 140. 
     In FIG. 3 a wire 342, forming part of cable 100, is connected to one contact 330 of set 320. The other contact 330 of set 320 is connected to one end of a wire 344, forming part of jumper cable 160, whose opposite end is connected to a contact 331 of set 321 in output block 140. Another contact 331 in set 321 is connected to one end of a wire 346, which forms part of cable 105. 
     To &#34;connect&#34; a subscriber, technicians typically provide three jumper cable pairs 347, 348 and 349. As shown in FIG. 1, the first jumper cable pair 347 connects an individual A node to an individual B node, in an MDF assigned to service the subscriber. The second jumper cable pair 348 connects an individual C node to an individual D node, in a cross-connection cabinet assigned to service the subscriber. The third jumper cable pair 349 connects an individual E node to the subscriber&#39;s F node in the distribution box assigned to service the subscriber. 
     The numbers of nodes per level specified above may vary from network to network. However, they exemplify a flexible network structure which allows for unpredictable and nonuniform demand for telephone lines. In the above example, the B:A interconnection has a flexibility factor of 20,000/10,000=2. The B:C interconnection is fixed. The D:C interconnection has a flexibility factor of 600/400=1.5. The F:E interconnection is fixed. The E:F interconnection has a flexibility factor of 120/60=2. 
     Therefore, there are three types of flexible interconnections in a typical telephone network, which are termed herein the A:B, C:D and E:F interconnections. 
     To maintain a telephone network, records of flexible interconnections are kept which indicate, for the A:B interconnections, which A node is connected to which B node, and similarly for the C:D and E:F interconnections. These records are often inaccurate because technicians sometimes do not interconnect the levels as instructed whereas the records are based on the interconnection instructions as given. Also, during repairs, the technician may need to change the connections and may neglect to report these changes. 
     For each subscriber line, the telephone company conventionally maintains a routing record including the following information: 
     a. Telephone line number; 
     b. The physical locations of the nodes assigned to the telephone line on each of levels A-F. The information stored to identify a physical location of a node typically comprises: 
     i. A cross-connect identifier, which is the identity of the cross-connection frame in which the node is located; and 
     ii. A pair number within the cross-connection frame. 
     Applicant/Assignee&#39;s Published European Application No. 93304514.8-2211 (Publication No. 0575100) describes a LAN connectivity scanner system operative to monitor connectivity of a local area network. 
     Published French Application No. 2680067 (National Registration No. 9109809) describes an optical device for monitoring connectivity of a multi-junction system which has applications for telecommunications. 
     Micro Computer Systems, Inc. 3708 Alliance Drive, Greensboro, N.C. 27407-2030, markets test equipment known as Remote Test Unit (Models 105A, 107A/F) which tests connectivity of active telephone lines. 
     Published UK Patent Application GB 2236398A (Application No. 8922025.5) describes a self documenting patch panel which documents the connections between input and output ports of a patch panel. The method of operation includes providing each input port with an input polling terminal and each output port with an output polling terminal and connecting an input polling terminal to an output polling terminal when the corresponding input and output ports are connected. A polling signal is sent to each input terminal in turn and the output terminal at which the polling signal is received is detected and is associated with the input terminal at which the polling signal originated. 
     Various types of shoe assemblies or connection blocks are known for use in telecommunications cross-connection blocks for over-voltage protection and line testing. A wide variety of these devices are commercially available from Krone of Germany. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide improved apparatus for monitoring routing of a cabling plant used for telecommunications, power, signaling, and other uses. 
     There is thus provided in accordance with a preferred embodiment of the present invention an interconnection monitoring system for use with a multiple node wired network, the system comprising a plurality of transmitters, each located at a node of the network for transmitting a transmission from the node and a plurality of receivers, each located at a node of the network, for receiving a transmission at the node, the plurality of transmitters being operative to transmit along the network a signal bearing an identification code identifying the node from which a transmission takes place, the plurality of receivers being operative to receive transmissions from a plurality of nodes, bearing the identification codes and thus indicating the interconnection status of the nodes. 
     Preferably, the plurality of receivers includes a plurality of memories for storing at least part of the transmissions received thereby. 
     In accordance with a preferred embodiment of the present invention, at least some of the plurality of transmitters and the plurality of receivers are configured as transceivers. 
     Preferably, the system also includes a central unit operative to synchronize the operation of the plurality of transmitters. The central unit preferably is operative to synchronize the operation of the plurality of transmitters on a hierarchical basis. 
     In accordance with one embodiment of the present invention, the network is a communications network and the plurality of transmitters are operative to transmit over the communications network in a manner which does not substantially interfere with communications thereover. 
     In accordance with another embodiment of the present invention, the network is a non-communications network and the plurality of transmitters are operative to transmit over the non-communications network in a manner which does not substantially interfere with the operations of the non-communications network. 
     For example, the network may be an electrical power supply network and the plurality of transmitters may be operative to transmit over the power supply network in a manner which does not substantially interfere with the power supply operations of the power supply network. 
     In accordance with a preferred embodiment of the present invention, the network is a telephone network and the plurality of transmitters are operative to transmit over the telephone network in a manner which does not substantially interfere with telephone communications thereover. 
     In accordance with an embodiment of the invention, the telephone network includes a main distribution frame, a plurality of cross-connect cabinets and a plurality of distribution boxes; and the plurality of transmitters and the plurality of receivers are located in at least one of the main distribution frames, a plurality of cross-connect cabinets and a plurality of distribution boxes. 
     In accordance with an embodiment of the invention, the telephone network includes a main distribution frame, a plurality of cross-connect cabinets and a plurality of distribution boxes; and the plurality of transmitters and the plurality of receivers are located in the main distribution frame, in plural ones of the plurality of cross-connect cabinets and in plural ones of the plurality of distribution boxes. 
     Preferably, the main distribution frame, plurality of cross-connect cabinets and plurality of distribution boxes comprise connection blocks to which network wires and patch wires are connected; and the plurality of transmitters and the plurality of receivers are connected to the connection blocks by means of auxiliary wires. 
     In accordance with a preferred embodiment of the present invention, the auxiliary wires are punched down on the connection blocks adjacent to the network wires. Alternatively or additionally, the auxiliary wires may form an integral part of the connection blocks. 
     Preferably, the main distribution frame, plurality of cross-connect cabinets and plurality of distribution boxes comprise connection blocks to which network wires and patch wires are connected; and the plurality of transmitters and the plurality of receivers are connected to the connection blocks by means of auxiliary wires fixedly connected to shoes mounted onto the connection blocks. 
     Preferably, the shoes are permanently fixed to the connection blocks. Alternatively, the shoes are removably mounted onto the connection blocks. 
     In accordance with one embodiment of the present invention, at least some of the plurality of receivers and the plurality of transmitters are portable. 
     Preferably, the shoes include visible indicators which are responsive to received signals from the plurality of transmitters. 
     In accordance with a preferred embodiment of the present invention, the plurality of transmitters provides in-band transmissions. Alternatively or additionally, the plurality of transmitters provides out-of-band transmissions. 
     Preferably, the plurality of transmitters provides information regarding the operational status of at least one of the main distribution frame, plurality of cross-connect cabinets and plurality of distribution boxes. 
     In accordance with a preferred embodiment of the present invention, the plurality of transmitters provides information regarding the electrical parameters of the network. Alternatively or additionally, the plurality of transmitters provides information regarding faults in the network. 
     Further in accordance with a preferred embodiment of the present invention there is provided a wired network comprising an interconnection monitoring system of the type described hereinabove. 
     Additionally in accordance with a preferred embodiment of the present invention there is provided an interconnection monitoring method for use with a multiple node wired network, the method comprising: providing a plurality of transmitters, each located at a node of the network for transmitting a transmission from the node, providing a plurality of receivers, each located at a node of the network, for receiving a transmission at the node, causing the plurality of transmitters to transmit along the network a signal bearing an identification code identifying the node from which a transmission takes place, and causing the plurality of receivers to receive transmissions from a plurality of nodes, bearing the identification codes and thus indicating the interconnection status of the nodes. 
     In accordance with a preferred embodiment of the present invention, the method also includes storing at least part of the received transmissions. 
     Preferably, at least some of the plurality of transmitters and the plurality of receivers operate as transceivers. 
     In accordance with a preferred embodiment of the present invention, the method also includes synchronizing the operation of the plurality of transmitters. Preferably, the synchronizing operates on a hierarchical basis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood and appreciated from the following detailed description, taken in conjunction with the drawings in which: 
     FIG. 1 is a simplified block diagram of a conventional prior art telephone network; 
     FIG. 2 is a simplified pictorial illustration of a conventional prior art cross-connection frame; 
     FIG. 3 is an illustration of a pair of individual contact sets interconnected by a conventional jumper cable or patch wire in accordance with the prior art; 
     FIG. 4 is a simplified block diagram of a telephone network the connections of which are automatically monitored in accordance with a preferred embodiment of the present invention; 
     FIG. 5 is a simplified illustration of the physical connection between a scanner and its corresponding termination block in the apparatus of FIG. 4; 
     FIG. 6 is a simplified functional block diagram of a scanner constructed and operative in accordance with a preferred embodiment of the present invention and useful in the apparatus of FIG. 4; 
     FIG. 7 is a simplified diagram of power and communication links of a central control unit residing in the regional telephone exchange of FIG. 4; 
     FIGS. 8A, 8B and 8C are illustrations of three interconnection structures useful in the apparatus of FIG. 4; and 
     FIG. 9 is a partially cut-away simplified pictorial illustration of a connection block constructed and operative in accordance with a preferred embodiment of the present invention. 
     Attached herewith are the following appendices which aid in the understanding and appreciation of one preferred embodiment of the invention shown and described herein: 
     Appendix A is a detailed description of the scanner of FIG. 6 including a scanner application software specification and net lists for the hardware components thereof; 
     Appendix B is a detailed description of the application software of control station 50, forming part of the apparatus of FIG. 7; 
     Appendix C is a net list of a power and communication hub, forming part of the apparatus of FIG. 7; and 
     Appendix D is a detailed description of a preferred set-up method, in which each scanner sensing wire is associated in the computer memory of the control station with an individual block which it will then monitor. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference is now made to FIG. 4 which illustrates a telephone network the connections of which are automatically monitored in accordance with a preferred embodiment of the present invention. 
     The apparatus of FIG. 4 is operative to monitor routing in a telecommunications system similar to the prior art telephone network of FIG. 1. For convenience, the reference numerals of FIG. 1 are employed to denote conventional components of the telephone network. 
     The present invention includes a plurality of scanners 40 each of which is operative to monitor a multiplicity of nodes on one or more levels and to report the connectivity status of each node to a control station 50 via a power and communication hub 60. The control station 50 is operative to accumulate the connectivity information from all of the scanners 40 and to generate periodically or on demand a routing table indicating the connectivity status of all nodes in the system. A preferred connection scheme between the control station 50, hub 60 and scanners 40 at all levels of the system is described in detail below with reference to FIG. 7. 
     The control station 50 is preferably operative to synchronize operation of the scanners 40. Typically, the control station 50 commands all scanners at a particular level (A, B, C, D, E or F, as shown in FIGS. 4 and 7) to enter a Tx (transmitting) mode. All scanners at all remaining levels are commanded to go into an Rx (Receiving) mode. This ensures that, for every multi-level link, i.e. a link which spans more than two levels, the scanner at one of the levels is transmitting and the scanners at all other levels are receiving. 
     Each Rx mode scanner searches for a synchronization signal, by scanning all of its nodes within the time interval for which each Tx mode scanner transmits a synchronization signal over an individual node. Upon detection of a synchronization signal, the scanner in Rx mode awaits receipt of transmitting scanner identification information from the same link and stores this information, which is subsequently reported to control station 50. 
     Scanners 40 are preferably also operative to provide alarm indications which relate to events in the MDF 11, CC Cabinets 20 and Distribution Boxes 30 or their vicinity. 
     FIG. 5 is a simplified illustration of a preferred method for physically connecting a scanner to a corresponding termination block. For simplicity, the reference numerals of prior art FIG. 3 are employed to denote the conventional components of the telephone network. 
     At least one scanner 40, functionally described below with reference to FIG. 6, is provided per cross-connection frame which it is desired to monitor. The scanner 40 may be connected as follows: 
     a. Connecting, as shown in FIG. 5, for each contact set 320 of each input block 120 being monitored, one end of an input scanning wire 350 to the contact 330 which is being used to connect input wire 342 to that contact set and connecting the other end of the input scanning wire 350 to an input of scanner 40. 
     Alternatively, the input scanning wire 350 may be connected to a third contact 330 (not shown), i.e. a contact not being used to connect to an input wire and not being used for a jumper cable wire; and 
     b. Connecting, for each contact set 321 of each output block 140 being monitored, one end of an output scanning wire 360 to the contact 331 which is being used to connect that contact set to output wire 346 and connecting the other end of the output scanning wire 360 to another input of scanner 40. This connection is not shown in FIG. 5. 
     Alternatively, as shown in FIG. 5, the output scanning wire 360 may be connected to a third contact 331, i.e. a contact not being used to connect the output wire and not being used for a jumper cable. 
     It is appreciated that, alternatively, the scanner may be employed to monitor only input blocks, rather than input blocks and output blocks. In this case, the input scanning wires 350 and the output scanning wires 360 are connected to input blocks. Similarly, if only output blocks are being monitored, the input and output scanning wires 350 and 360, respectively, are connected to output blocks. 
     Reference is now made to FIGS. 8A-8C, which illustrate alternative connection techniques useful for physically connecting a scanner to a corresponding termination block. 
     FIG. 8A illustrates connection of a metallic shoe element 362, which is connected to an input or output scanning wire 364, to a contact 366 specially configured to conform to the configuration of shoe 362. Shoes 362 and contacts 366 of this type are known in the prior art. It is noted that shoes 362 may simultaneously contact a plurality of contacts 366. 
     FIG. 8B illustrates connection of a printed circuit board element 372, which is connected to an input or output scanning wire 374, to an interruptible double contact 376, specially configured to conform to the configuration of printed circuit board element 372. Printed circuit board elements 372 and contacts 376 of this type are known in the prior art. Printed circuit board elements 372 may simultaneously contact a plurality of contacts 376. 
     FIG. 8C illustrates a printed circuit board assembly 382 of novel construction, which connects multiple input or output scanning wires 384 to multiple conventional contacts 386, via contacts 387. Conventional contacts 386 need not be specially configured to conform to the configuration of assembly 382. Alternatively contacts of the type indicated by reference numerals 366 (FIG. 8A) or 376 (FIG. 8B) may be employed. 
     In accordance with a preferred embodiment of the present invention, printed circuit board element 382 may also include visual indicators, such as LEDs 388 to identify particular nodes requiring attention by a technician for connection, disconnection or maintenance. 
     Additionally, the printed circuit board assembly 382 may include monitoring terminals 389, coupled to contacts 387, to enable monitoring equipment to be attached thereto for monitoring given nodes, without requiring removal of the assembly 382 from contact with contacts 386. Reference is now made to FIG. 9, which illustrates a novel connection block 352 constructed and operative in accordance with a preferred embodiment of the present invention. The connection block 352 comprises a housing 353 which surrounds a printed circuit board 354 onto which are mounted an array of conventional contacts 355. The printed circuit board 354 connects each of the conventional contacts 355 to a corresponding contact within a standard DB-25 connector 356, which may be readily and removably connected to a scanner 40. 
     Returning now once again to FIG. 5, it is noted that once the scanner 40 has been installed within a cross-connection frame, a set-up procedure may be employed to create an information table which associates each scanner input or output with the corresponding individual cross-connection frame connection point to which it is connected. 
     Preferably, this information table is accumulated by a portable computer 370, termed herein a set-up computer, and is subsequently transferred to the control station 50. A preferred set-up method is as follows: 
     a. Set-up computer 370 is connected via its RS232 port to an RS232 interface 520 (FIG. 6) of the scanner 40. 
     b. Set-up box 380 is connected to a multi-pair set-up adapter 390 and to set-up computer 370. The multi-pair set-up adapter 390 may be of the type illustrated in any of FIGS. 8A-8C and is operative to removably connect the set-up box 380 and computer 370 to a multiplicity of contacts 330 and 331 within respective blocks 120 and 140. 
     c. The software of set-up computer 370, which is described in detail in Appendix D, prompts the user to connect the multi-pair set-up adapter 390 to a specified block in the cross-connection frame. The operator is asked to enter the cross-connection frame identifier and the capacity of the cross-connection frame. 
     d. The set-up computer 370 instructs the set-up box to sequentially transmit a predetermined Tx signal over the contacts 330 and 331 corresponding to the pairs now undergoing the set-up process. At the same time, scanner 40 is instructed to enter the Rx mode in order to receive and store the Tx signals sent by the set-up box. Once the set-up box has finished transmitting over all the pairs undergoing set-up, the set-up computer instructs the scanner to send the identity of the ports on which the set-up box signals were received. These identities are accumulated and eventually transferred to the control station 50. 
     e. The software of the set-up computer 370 then prompts the user to repeat steps c. onward for each of the remaining blocks in the cross-connection frame until the connectivity status of each of the blocks has been accumulated. 
     It is appreciated that the scanners 40 are retrofittable to existing networks. According to one embodiment of the present invention, a scanner is permanently installed in each cross-connection frame. Alternatively, some of the cross-connection frames may not be provided with a permanent scanner. Instead, a single portable scanner or small number of portable scanners may be employed to sequentially monitor some or all of the cross-connection cabinets and distribution boxes. 
     In accordance with this embodiment of the invention, a technician conveys the portable scanner from one cross-connection frame to another. At each frame, the portable scanner may be temporarily connected to the frame in a manner similar to the manner in which the set-up computer is connected (FIG. 5). Alternatively, the connection may employ the apparatus of any of FIGS. 8A-8D. 
     Two modes of operation using a portable scanner are envisioned: 
     In one mode of operation, here termed a &#34;network test mode&#34;, the portable scanner, once installed, communicates with the control station 50 in accordance with a predetermined protocol, requests that all other scanners at other levels be transferred to the Rx mode and obtains permission to transmit a signal to the other scanners. The operation of the scanner in this mode is identical to the operation of a permanent scanner as described hereinabove. 
     In another mode of operation, here termed a &#34;local test mode&#34;, the portable scanner, once installed, need not communicate with the control station 50, but rather communicates with different levels within the single cross-connection frame to which it is connected. The portable scanner may store the local test results for eventual download. 
     FIG. 6 is a simplified functional block diagram of a scanner constructed and operative in accordance with a preferred embodiment of the present invention. The scanner of FIG. 6 includes two switching transceivers 400 and 410 each of which functions either as a transmitter or as a receiver as commanded by a microcontroller 420 via a data/control bus 430. This architecture allows the scanner to monitor two levels within an individual cross-connection frame even when one of the two levels is transmitting and the other of the two levels is receiving. 
     Transceiver 400 comprises a plurality of connectors 440 to which the input wires 350 or output wires 360 (FIG. 5) are connected. All wires connected to connectors 440 are of the same type, i.e. either all input wires or all output wires. 
     Connectors 440 are coupled via suitable protection circuitry 444 to a switching circuit 450, the operation of which is controlled by microcontroller 420 via bus 430. Switching circuit 450 is operative to selectably connect any pair of wires 350 or 360, as the case may be, to an activity sensor 460 and via a modem 470 to a UART, asynchronous receive/transmit circuit 472. Circuitry 460, 470 and 472 are also coupled to microcontroller 420 via bus 430. 
     Transceiver 410 comprises a plurality of connectors 480 to which the input wires 350 or output wires 360 (FIG. 5) are connected. All wires connected to connectors 480 are of the same type, i.e. either all input wires or all output wires. 
     Connectors 480 are coupled via suitable protection circuitry 484 to a switching circuit 486, the operation of which is controlled by microcontroller 420 via bus 430. Switching circuit 486 is operative to selectably connect any pair of wires 350 or 360, as the case may be, to an activity sensor 488 and via a switch 490 and a modem 492 to a UART, asynchronous receive/transmit circuit 494. Circuitry 488, 490, 492 and 494 are also coupled to microcontroller 420 via bus 430. 
     Each transceiver 400 or 410 performs the following two operations: 
     a. Receiving operation--The transceiver scans all lines connected to it by activating switching circuit 450 or 486, which connects each line in turn to activity sensor 460 or 488. If the activity sensor 460 or 488 detects a signal on the line, this is reported to the microcontroller 420 which activates modem 470 or 492 to determine if the signal is a valid Tx signal. If so, further switching does not take place until the contents of the valid Tx signal is transferred to the microcontroller 420 via modem 470 or 492 and UART 472 or 494. 
     b. Transmitting operation--The microcontroller 420 commands the switching circuit 450 or 486 sequentially to connect each pair of wires 350 or 360 to activity sensor 460 or 488. If the activity sensor 460 or 488 detects a signal on the line, this is reported to the microcontroller 420 which notes that such line is busy and causes the switching circuit to move on to the next line. If no activity is reported on a given line the microcontroller 420 causes the modem 470 or 492 to transmit initially a Tx synchronization signal followed by a Tx signal. 
     Transmission and reception may be carried out in a frequency band not utilized for other communication (out-of-band) to allow the scanners to operate in parallel to transmission of other information, such as voice and fax information, over the lines. Alternatively, transmission and reception may be carried out in the same frequency band as other communication (in-band) provided that a line activity circuit ensures that an individual line is not being used before transmitting over that line. 
     The Tx signal preferably comprises: 
     a. An indication of the level (A, B, C, D, E or F in FIG. 4) of the scanner; 
     b. An ID of the transmitting scanner; 
     c. An ID of the currently transmitting wire pair from among the pairs monitored by the scanner. 
     Referring now once again to FIGS. 4, 6 and 7 which illustrate power and communication hub 60, it is noted that a single wire pair connected to hub 60 is coupled to each scanner 40 via a wire pair either of cable 14 or of cable 24. The wire pair is connected via a splitter circuit 496 which receives a high voltage over the wire pair and supplies it to a power supply (not shown) which transforms it to appropriate voltages for use throughout the scanner circuitry. 
     Splitter circuit 496 also provides communication signals to modem 492 via switch 490. Switch 490, controlled by microcontroller 420, is operative to determine whether the modem 492 receives communications from or transmits communications to the power and communication hub 60 of FIGS. 4 and 7, or alternatively whether the modem 492 receives or transmits over wires 350 or 360 via switching circuit 486. Each scanner 40 may optionally also include apparatus for indicating faults in the network and measuring various electrical parameters thereof. Such apparatus may be connected to the switching circuit 450 or 486 in parallel with the activity sensor 460 or 488. 
     Each scanner 40 preferably also includes RS232 interface circuitry 520 which allows communication with a laptop or similar computer which is employed for set-up as described in detail herein with reference to Appendix C, testing or download. 
     Optionally, each scanner 40 may include alarm sensing circuitry 530 which alerts the control station 50 of events occurring in the vicinity of the cross-connection frame, which affect the operational status thereof. Preferably, the alarm sensing circuitry 530 is operative to: 
     a. Alarm if the CC cabinet or distribution box door is opened; and/or 
     b. Alarm if a unacceptable temperature, smoke or fire are detected within the CC cabinet or distribution box. 
     Appendix A is a detailed description of a scanner 40 constructed and operative in accordance with a preferred embodiment of the present invention. 
     FIG. 7 is a diagram of the power and communication links of the scanners 40 with the hub 60 and the control station 50 of FIG. 4. As described above, the control station 50 typically resides at the regional telephone exchange 10 (FIG. 4) which is operative to receive from each scanner the connectivity status of all nodes monitored thereby and to generate a routing table representing the connectivity status of all nodes in the network. 
     Typically, the control station 50 downloads all information from all scanners periodically, such as once a day, and creates an integrated connectivity database. The control station 50 may, for example, generate a comparison of today&#39;s routing with yesterday&#39;s routing. Preferable, the control station 50 continuously operates a scanning functionality in the hub 60, similar to that described hereinabove with reference to the Rx operation of the scanner 40. This functionality enables the control station to promptly receive alarms and other messages from the various scanners 40. 
     Appendix B is a detailed description of the control station 50 of FIG. 7. 
     The control station 50 is preferably operative to identify vacant wire pairs in each CC cabinet, to identify fully occupied CC cabinets, and to identify faulty cables and disconnections in CC cabinets, as described in detail in Appendix B. 
     The control station 50 requires little maintenance time and is easy to install. Following a one-time installation, routing information is generated automatically. 
     A preferred set-up method, in which a table is generated in memory which links physical connections of the scanner and actual block designations or numbers, is described in Appendix C. 
     It is appreciated that the software components of the present invention may, if desired, be implemented in ROM (read-only memory) form. The software components may, generally, be implemented in hardware, if desired, using conventional techniques. 
     It is appreciated that the particular embodiment described in the Appendices is intended only to provide an extremely detailed disclosure of the present invention and is not intended to be limiting. It is appreciated that various features of the invention which are, for clarity, described in the contexts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable subcombination. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention is defined only by the claims that follow: ##SPC1##