DE4421615C1 - Circuit arrangement for external interference protection for the wired telephone network - Google Patents

Description

The invention relates to a circuit arrangement for protection against external interference in a wired telephone network with cable cores using modular components nen between a telephone exchange, which is a main distributor and a subscriber Mer connection unit, and one connected to a TAE outlet Telephone equipment, in particular a telephone set, are arranged.

In the wired telephone network according to its current structure with line wires a and b is designed when a telephone subscriber dials a telephone number following connection establishment between this subscriber and a telephone exchange. When the telephone subscriber picks up the telephone handset, a line appears loop between his telephone and the telephone exchange that is connected to you Main distributor and a subscriber line unit is formed. The education this loop leads to a current flow between the line wires a and b, so that in the subscriber line unit of the telephone exchange registers the structure of the loop becomes. From the telephone exchange, a prompt for the telephone set of the Telephone subscriber sent. The telephone subscriber can now choose Make the desired number. Each digit selected is marked with a be number of loop breaks or, depending on the electoral process, by an ent speaking number of frequency impulses with defined length and frequency (IWF = pulse dialing method), a tone corresponding to the number (DTMF = multifrequ quenzverfahren) or a frequency mix corresponding to the number (MFC = Mehrfre characterization). After the electoral process has been completed, this takes place Send the call sign or a busy signal. The selected participant answers mer, the connection establishment is completed. After the end of the call, the Triggering the connection path and thus interrupting the line loop, by one of the two subscribers picking up the receiver of his telephone set sets. The weakness of this type of connection is that the structure of the required loop at any point between the telephone exchange and a telephone set by simply establishing a connection between the Line wires a and b can be made. The telephone exchange facilities can do not differentiate where and by whom the line loop is formed. The  The line loop can be formed, for example, simply by being clamped on a telephone in the appropriate place and picking up his handset consequences. This fact is used, among other things, by telecommunications engineers during the inspection the line. However, it is also for any unauthorized user of the Telephone network the possibility of entering the network and making calls Costs of authorized telephone subscribers given.

Various protective devices are known which act against an unauthorized person particularly vulnerable areas, preferably on line distributors, for example in Residential buildings of a telephone subscriber are arranged to prevent. Here these devices are protected by mechanical locks. Also locks for the telephone itself, on which only arrives in the event of a block Calls can be answered, or for the TAE junction box are known. However, these protective devices offer only very limited protection and restrict also partially the authorized telephone subscriber. For an intrusion Mechanical locks are just a relatively easy obstacle to overcome especially when manipulations are carried out undisturbed can, as is often the case with the line distributors generally arranged in the basement Case is. After removing the mechanical obstacle, it is for an intruder no longer a problem, the telephone network for its purposes in the manner described use.

For the reasons mentioned, complaints have been increasing recently that of telephone subscribers about unauthorized use of the telephone network your costs. A piece of evidence of the calls made by a connection can In the best case scenario, only make unauthorized use recognizable, however do not prevent.

DE PS 34 12 590 discloses a circuit arrangement for a telephone set. This circuit arrangement, which the adaptation of a telephone set to their Use requires, allows for certain selected phone numbers of dialing. The disclosed arrangement, however, only the Misuse of the telephone set itself prevented in a desired manner. A abusive parallel assignment between a telephone exchange and the telephone set advice is neither determined by the circuit arrangement according to the disclosed teaching still prevented.  

The same applies to the device disclosed by EP 0 560 217. This also prevents only an unauthorized access to the telephone itself and requires for their effectiveness also takes a variety of actions by an authorized user. For the authorized user is thus made more difficult to use his telephone set.

DE PS 37 15 580 is a circuit arrangement for monitoring a Telephone line disclosed. The arrangement requires a change to exist the telephones in that an additional Contact is provided, which is connected to the control device of the telephone set that is. As a result, this circuit arrangement is not suitable for simple retrofitting existing telecommunications technology. In addition, the circuit arrangement is so concise piert that through it an abusive parallel assignment between the telephone office and the telephone set is recognized, signaled and significantly disturbed, however is not completely prevented. The doctrine also does not convey like an unwarranted one te parallel assignment can be prevented with a telephone set, which also has the circuit according to the invention. The same applies to technology known in France cal devices for monitoring line distributors that are only detecting serve an unauthorized parallel assignment.

The invention has for its object a circuit arrangement of the generic type he way of creating unauthorized access between the telephone exchange and long distance excludes speech device, user-friendly, inexpensive and independent of the operating system gig is usable and both a simple retrofitting of existing telephone systems, as well as integration into new systems.

According to the invention the object is achieved in that in a circuit arrangement to protect against external interference in a wired telephone network with line wire using module components that are between a telephone exchange, which has a main distributor and a subscriber line unit, and one a TAE junction box connected telephone device, especially one Telephone apparatus are arranged that a module construction to form a control system stone A in front of the main distributor of the telephone exchange and a module B between the TAE junction box and the telephone set and both to Lei  tungsadern a and b are connected that in the event of legitimate use of the Telephone network a line loop between the telephone set and the telephone office with the inclusion of module modules A and B and one between them the exchange of their matching identifiers for identification purposes det is and that in the event of unauthorized use, a line loop between the place of unauthorized use and the telephone exchange including the Module block A, but not including module block B and the exchange an identification identifier is formed.

In an advantageous embodiment of the invention, the module modules A and B are theirs Power supply connected to the line voltage on the line wires a and b sen.

The circuit arrangement according to the invention is particularly advantageous if the module blocks A and B have a constantly changing identifier.

A further advantageous embodiment of the invention is given in that the control system formed in modules A and B in a simple retrofit existing facilities enabling way is trained.

It is also an advantage of the circuit arrangement according to the invention that the Kon troll system is designed in a way that enables integration into new systems.

It is an advantage of the invention that in the event of legitimate use of the remote sprechnetzes the control system formed from modules A and B in any case in the Connection establishment is included, which provides almost absolute protection against you unauthorized access between the telephone exchange and the TAE junction box on the remote speaker is guaranteed. By including the module components in the Line loop is always forced to compare their identifiers. In this way it ensures that a signal to request the formation of the loop effecting person only if the comparison result is positive, i.e. if they agree the identifier is sent and otherwise a blocking or a separation of the Line is carried out and optionally a busy signal is placed on the line. One possible intruder, which creates the formation of a loop anywhere between  the telephone exchange and the TAE junction box of a subscriber works, it is made impossible to use the system for itself, because the module Module B is not included in the line loop and the unauthorized party the does not know the encoding.

Due to its simple principle, the circuit arrangement is largely independent of the operating system hanging design. The module blocks A and B can be easily executed so that you at any time in accordance with the applicable technical standards, e.g. B. for quick connection technology, designed telephone network can be included. The circuit arrangement can be inserted into the existing telephone network without one of the ones currently in the distance used modules were discarded or the conception changed must become. Due to the design of the module blocks in a pluggable design existing systems can be easily retrofitted.

The module modules are designed so that when designing new systems, the Module A in the wiring of the main distributor or in the structure of the participants mer connection unit integrated and the module module B in the TAE junction box or Subscriber terminal can be designed pluggable.

It is particularly advantageous that the authorized user is one with the inventive Circuit arrangement equipped telephone terminal do not make any decisions or must carry out additional activities in order for the protection to take effect, since the circuit arrangement his telephone connection from him unnoticed and without Action monitored.

Due to the possibility of the circuit arrangement according to an advantageous off training in such a way that, in the event of legitimate use, the Module blocks A and B exchanged identifier by the circuit arrangement every loop formation is changed, a third party intervention is more difficult and practical table impossible. In this way it is impossible that during a legitimate Use the coding for the purpose of a later unauthorized external intervention is read out.

It is further advantageous in the sense of the invention that the module components A and B escape after successful participant identification or after ending a call ches return to the basic state, i.e. a sleep or standby mode.  

The invention will be explained in more detail using an exemplary embodiment. In the associated drawing show:

Fig. 1 The classification of the circuit arrangement according to the invention with the module blocks A and B in the telephone network

Fig. 2 The formation of a between a telephone exchange and a telephony device, such as a telephone, best existing loop according to the prior art.

Fig. 2 shows a between a telephone 9 and a telephone exchange 1 formed loop, which enables access to the telephone network in the manner shown in the explanation of the prior art and with the disadvantages mentioned. The facilities of the telephone exchange 1 can be of an analog or digital type. Shown is the telephone terminal 9 , which is initially connected via the line wires a and b to the TAE junction box 7 arranged in the rooms of the authorized subscriber. Both the telephone device 9 and the TAE junction box 7 are hen with known mechanical protection devices 8 and 6 verses. The TAE junction box 7 is also connected via the line wires a and b to a line distributor 4 . The line distributor 4 also has a mechanical protective device 5 . The connection to the telephone exchange 1 with the main distributor 2 and the subscriber line unit 3 is formed by the line distributor 4 via the line wires a and b.

In FIG. 1, the arrangement of the circuit arrangement according to the invention to protect against unauthorized interference in the wired telephone network. The inclusion of the circuit arrangement according to the invention is given in that the main distributor 2 and the subscriber line unit 3 in the telephone exchange 1 is assigned a module A 10 between the wires a and b and in the area between a TAE junction box 7 and the telephone device 9 a module B 11 is arranged, which is also connected to the line wires a and b. The modular component A 10 and the modular component B 11 form the control system 12 for protection against external interference by the exchange of data when the authorized subscriber forms a line loop, as shown in the table below:

The authorized telephone subscriber first forms by lifting his tele fonhörers a line loop.

This loop formation is detected by the module B 11 and activates the module B 11 . The loop leads to the transmission of the dial request sign from the telephone exchange 1 to the subscriber. However, the sign is initially suppressed by the module component A 10, which is also activated by the loop, by means of a filter circuit for the corresponding frequency. The module block A 10 requests the subscriber identifier from the module block B 11 via a request pulse. This identifier, the z. B. may consist of appropriately modulated signals, has a different combination for each combination of the module blocks A 10 and B 11 and is stored in the manufacture or set up of the circuit arrangement for protection against external interference in the modules.

The identifier then sent by module module B 11 is checked for validity by module module A 10 . If the subscriber is authorized, this validity is given and the filter circuit releases the request prompt. The participant can start with the election. In the event that the authorized subscriber begins with the election before the release of the election request sign, a buffer memory to be provided in the modular block A 10 could buffer the digits already dialed until the choice is released.

After successful identification or after hanging up the handset at Ge At the end of the call, the initial state of the modules is established.

On the other hand, when a loop is formed between the telephone exchange 1 and the location of an unauthorized intervention, data is exchanged as shown in the table below:

In this case, unauthorized participants would, for example in the area between the TAE junction box 7 and the telephone exchange 1, pinch on the wires a and b of the connection and generate a line loop to the telephone exchange 1 by lifting the handset. The module B 11 does not recognize the loop because the module B 11 is not included in the loop. A disconnection of the line in the direction of the authorized subscriber does not lead to the inclusion of the module block B 11 , which therefore remains in the deactivated state in both cases. The module block A 10 recognizes the loop, suppresses the request prompt and sends a request impulse for the subscriber identification in the direction of the subscriber. The participant identification is not supplied by the deactivated module B 11 or offered by a possible module block B of the intruder in the wrong combination. After the module block A 10 has unsuccessfully requested the correct subscriber identification twice, the module module triggers switching processes that cause the Prevent unauthorized persons from dialing a number. The loop interruptions required to dial a number are prevented, frequency dialing pulses of all kinds are suppressed in the direction of the telephone exchange 1 or the loop formed is interrupted by actuators contained in the module component A 10 . The module module A 10 can send a busy signal towards the subscriber as a signal for the connection blocking. After placing the handset at the end of the intervention, the initial state of the module components 10 and 11 is established .

Thus, there is only the outgoing access authorization on its connection for the owner of the module B 11 . The power supply to the module blocks 10 and 11 ge occurs through the exchange voltage via the line wires a and b. In principle, all telephone devices of the type described in the introduction can be retrofitted with these module components 10 and 11 .

Various signal forms are available for the transmission of request impulse and subscriber identification. The number of possible combinations is so large that it is very unlikely that the identifications of the module component B 11 and that of a module component in the hand of an intruder will match at random. If necessary and corresponding technical expansion of the module blocks, changing identifiers are also possible after each loop formation, so that reading and the subsequent use of the identifier by the stranger leads to no success.

In the manufacture of telephony devices, the module B 11 can already be integrated in the telephony device 9 or in the TAE junction box 7 . The same applies to the A 10 module when setting up new telephone exchanges.

Data exchange in ISDN is exclusively digital, so that module components of the type described cannot be used. A possible protection can be implemented here by also providing a subscriber identification in the connection protocol between the subscriber and the telephone exchange 1 .

Reference list

1 - Telephone exchange
2 - Main distributor
3 - subscriber line unit
4 - line distributor
5 - mechanical protection device
6 - mechanical protection device
7 - TAE junction box
8 - mechanical protection device
9 - subscriber terminal, in particular telephone set
10 - Module block A
11 - Module block B
12 - Control system consisting of module blocks A and B

Claims (5)

1. Circuit arrangement for protection against external interference, in particular against unauthorized dialing of other call participants in a wired telephone network with line cores using module components which are between a telephone exchange, which has a main distributor and a subscriber line unit, and a telephone line connected to a TAE connection box direction, in particular a telephone set, are characterized in that, to form a control system ( 12 ), a module A ( 10 ) on the main distributor ( 2 ) with subscriber line unit ( 3 ) of the telephone exchange and a module B ( 11 ) between the TAE Junction box ( 7 ) and the telephone terminal device ( 9 ) are arranged and are each connected to both line wires a and b, that in the event of an authorized use of the telephone network, a line loop between the telephone device ( 9 ) and the telephone exchange ( 1 ) under egg Relation of the module blocks A ( 10 ) and B ( 11 ) and a between them, the identification serving exchange of their matching Ken identifications is formed and that in the event of unauthorized use by a parallel to the telephone terminal ( 9 ) pinching and dialing a phone number one Line loop is formed between the location of the unauthorized use and the telephone exchange ( 1 ) including the module module A ( 10 ), but not including the module module B ( 11 ) and the exchange of an identifier used for identification. 2. Circuit arrangement according to claim 1, characterized in that the modular building blocks A ( 10 ) and B ( 11 ) are connected to their power supply to the line voltage lying on the line wires a and b. 3. Circuit arrangement according to claims 1 and 2, characterized in that the module blocks A ( 10 ) and B ( 11 ) have a constantly changing identifier. 4. Circuit arrangement according to one of the preceding claims, characterized in that the control system ( 12 ) can be classified with a simple retrofit in existing systems. 5. Circuit arrangement according to one of the preceding claims, characterized in that the control system ( 12 ) is designed in a way that enables integration into new systems.