DE1211278B - Circuit arrangement for catching maliciously calling subscriber connections in telecommunications, in particular telephone switching systems - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H04m

German class: 21 a3-28 / 02

Number: 1 211 278

File number: T 26792 VIII a / 21 a3

Filing date: August 12, 1964

Launch day: February 24, 1966

The main patent application relates to a circuit arrangement for intercepting maliciously calling subscriber lines in telecommunications, in particular telephone exchanges, in which an interception device connected to the subscriber line to be protected contains means which respond when a call signal arrives and a catching earth potential preventing the triggering of the connection path by the calling subscriber to a speech wire in that a negative potential connected to the control wire c of the speech network through the interception device connected only to the subscriber line to be protected at the first ringing signal, after the subscriber has reported, delayed by the interception state initiating visual holding means Connection of earth potential is eliminated and that the connection sets or line selector of the exchange facilities for the evaluation of the temporal occurrence of the earth potential entials on the control wire c and for the connection of the Fanger ground potential to the speech wire α of the incoming connection path, which is dependent on the evaluation.

The invention relates to a further development of the object the main patent application.

In the case of interception systems, it can have an unfavorable effect that the frequency of the ringing current of 25 Hz is adjacent to the pulse frequency of 10 Hz of the number switch. That is the one to be protected Subscriber calling, he sends impulses by means of his number switch, if necessary be evaluated by the call receiver as a criterion for preparatory catching. Then contains the following Dialing digit sequence happens to be the catch digit, so the participant catches himself.

For the distinction between the number switch frequency and the calling frequency, one can, as is well known, Apply filters or bandpasses. However, these are expensive for the low frequencies mentioned.

In general, the ringing current is at a frequency of 25 Hz at intervals of nine seconds each sent for one second, approximately 25 periods per callsign. The one from the number switch On the other hand, transmitted pulses can at most with one digit, corresponding to a "zero", only be ten.

The invention is characterized in that a counting chain is provided which corresponds to that on the subscriber line incoming impulse or ringing frequency characters and only after reaching of a minimum count for an impulse attitude command to catch maliciously calling subscriber losses in telemetry, especially Fe'rnspfech'vermittianlagen

Addition to registration: T 26026 VIII a / 2l ä3 - Äüslegeschrift 1203 833

Ancestors:
Telefunkeri

Patent collecting society m. B. H., Ulm / Danube, Elisabethenstr. 3

Named as inventor:

Rudolf Morlang, Backnang;

Herbert Kle'psch, Bäcknang-Unterschöntal

series or for a ringing frequency signal the interception system switches to ready for reception.

The invention is explained using the circuit diagram.

The loop mode evaluation SAW described in the main patent application is used in the same way, but the evaluation transistor is replaced by the voltage-sensitive multivibrator with the transistors TsI and Ts2 . The relay E located in the collector circuit of the transistor TsI drops on the one hand when the loop current of the connected subscriber station is flowing and on the other hand due to the one polarity of the incoming ringing alternating current. His contacts! sends the impulses present on the subscriber line to the delayed relay V , which therefore drops out during the pauses between pulse series, ie while direct current flows in the subscriber loop. It is excited in the circuit:

- Relay V

^ ' ^J capacitor Cl, resistor R 1' rectifier Gr i, contact el, earth.

As long as the relay V keeps its contact ν closed, the counting chain IZ is switched on. The impulses of the subscriber line are fed through the contact part of the counting chain IZ:

(-), contacts, counting chain ΪΖ, contact v, earth.

The counting chain IZ used in the exemplary embodiment shown here is in a manner known per se

609 509/60

constructed as a binary counting chain and therefore does not need to be explained in more detail. Since it has four levels, it counts sixteen impulses and then emits an impulse to the call relay R , which is thereby energized. With the first call the relay HR picks up in the circuit:

(-), relay HR, contact rl, control wire c, to connection set VSB, contact pl, relay windingPI, contact el, earth.

The relay Hi? maintains itself through its own contact hrl, while its contact Ar II armed the interception device in the manner known from the main patent application.

If, on the other hand, the counting chain IZ receives a series of pulses from a number switch, i.e. a maximum of ten pulses, the counting chain does not go through to the call relay R and the interception system is not armed. Since after each pulse series the relay. F falls and the counting chain IZ switches off with its contact ν, this starts counting from the starting position at the beginning of each new pulse series.

If the interception system has been armed and the subscriber TIn to be protected has reported, the receiving relay £ in the loop current evaluation SAW drops out. Contact el de-energizes relay F, which drops out after the specified delay. When the contact ν is opened, the relay VR, which has been short-circuited until then, is released:

(-), resistor R 2, relay VR, earth.

At the same time, the excitation of the drop-out delayed relay VH is also removed.

If the relay VR has closed its contact vr and the drop-out delayed relay VH has not yet opened its contact vh , the relay FH is energized:

(-), relay FH, rectifier Gr4, contact vr, contact vh, contact ArII, earth.

The relay FH is maintained through its contact // ill, since the relay T of the electronic timer is energized and keeps its contact t closed.

(-), relay FH, contact *, rectifier GrS, contact fh Π, button AT, contact kr Π, earth.

At the same time, the contact / MI short-circuits the relay TH , the contact th of which enables the electronic timer Zg to expire, which after about 30 seconds switches off the temporarily applied trap indicator from the control wire c of the subscriber line, because the contact t of the relay T is the holding circuit of the relay FH interrupts.

If the subscriber TIn to be protected feels annoyed by a call, he dials the so-called catch digit, in this example it is "two". The number switch interrupts the loop current and the relay E of the loop current evaluation & ilF picks up twice.

As soon as the first pulse occurs, relay V is energized via contact el . It is held during the pulse pause due to its dropout delay. With the contact ν the relay Fi? energized, whose contact vh switches on the counting chain 2 Z for paying off the catch digit:

(-), counting chain 2Z, contact vh, contact hr II, earth.

If the correct catch digit is recorded in the counting chain 2Z 'via the contact e III, the relay 2Zö and its contact 2 zα are activated and the catch relay F is energized:

(-), resistor, relay F, contact 2za, rectifier Gr 7, contact vr, contact vh, contact hr II, earth.

The relay maintains its own contact / II:

(-), resistor, relay F, rectifier size 8, contact / II, button AT, contact hr II, earth.

The contact / I places the trap indicator on the control wire c in a known manner.

Each time the contact vh drops , the counting chain 2Z is switched off and returned to its starting position.

Claims (2)

Patent claims: 1.Circuit arrangement for catching maliciously calling subscriber connections in telecommunications, in particular telephone switching systems, in which an interception device connected to the subscriber line to be protected contains means which respond when a call signal arrives and a catching ground potential to prevent the triggering of the connection path by the calling subscriber Put on the speech wire in that a negative potential connected to the control wire c of the speech network in the interception device connected only to the subscriber line to be protected at the first call signal, after the subscriber has reported, delayed by the interception state initiating switching means by connecting Ground potential is eliminated and that the connection sets or line selector of the exchange facilities for the evaluation of the temporal occurrence of the ground potential on the control wire c and for contain the connection of the intercepting ground potential, which is dependent on the evaluation, to the speech wire a of the incoming connection path, according to patent application T 26026 VIII a / 21 a », characterized in that a counting chain (IZ) is provided which contains the information on the subscriber line (TIn, Sta, Stb) counts incoming pulse or ringing frequency signals and only switches the interception device ready for reception after reaching a minimum count for a pulse series or for a ringing frequency signal. 2. Circuit arrangement according to claim 1, characterized in that the counting chain (IZ) returned to their original position after each pulse series or after each call sign will. 1 sheet of drawings 609 509/60 2.66 © "Bundesdruckerei Berlin