DE2838629A1 - Loop current interruption system for subscriber circuits - uses clock pulse generator to drive relay, via flip=flop and counter, which opens line contact to break loop current - Google Patents

Abstract

The interruption circuit comprises a timer switch (ZSE) which controls a normally-closed contact (f) in the 'b' leg of the station circuit (SS). The control unit consists of a clock-pulse generator (TG) incorporating a frequency standard, which is connected to a counter (Z). When a start button (T) is operated, te counter runs for a certain time. The counter has a number of outputs which can be connected to a gate (G). A flip-flop is set on the first count pulse and its amplified output (v) activates a relay (F) which then opens the line contact (f) to break the loop current. When the required count is reached, the flip-flop is reset and the relay drops out. The loop current is restored. If the subscriber station is fitted with a digital frequency oscillator for multiple-frequency dialling (TG') the clock-pulse generator is not required.

Description

Circuit arrangement for subscriber stations in telecommunications

de-, in particular telephone systems, for time-defined interruptions of the loop current The invention relates to a circuit arrangement for subscriber stations in telecommunication systems, in particular telephone systems, for time-defined interruptions of the loop current.

In telephone exchanges, especially when using the multi-frequency touch-dial method, The task often arises during an existing connection additional to transmit switching data from the subscriber station to a control center, e.g.

to initiate queries or to transfer the existing call. Such switching-related data are in the form of a precisely defined time Transfer interruption of the loop current.

For the time-defined interruption of the loop current are mechanical Arrangements known. These are knew mechanical devices require a relatively large amount of space in the subscriber station and are in theirs Structure very complicated, which leads to a high susceptibility to failure. As another Another disadvantage is that expensive injection molding tools are required for their manufacture are.

There are also known electrical devices in which the time-defined interruption of the loop current by means of an RC timing element he follows.

The disadvantage of the two known devices for the defined time Interruption of the loop current consists in the fact that long interruption times, e.g.

greater than 200 ms, no more or no longer with sufficient accuracy can be generated.

The object of the invention is to provide a circuit arrangement of the type mentioned at the beginning, with a relatively simple structure Time-defined loop current interruptions of any desired duration with the greatest Accuracy allowed.

According to the invention, this object is achieved in that in series with the actual station circuit, a break contact is arranged in the loop circuit and the opening time of the normally closed contact of a clock pulse generator with a timer containing a frequency standard is controlled.

The circuit arrangement according to the invention is characterized by this from that the required loop current interruptions with the greatest possible accuracy can be complied with. Even with long loop current interruptions, anyone can required accuracy can be achieved. With today's integrated circuit technology results For the circuit arrangement according to the invention there is still a simpler and more space-saving one Construction.

An expedient development of the invention for subscriber stations with a digital frequency oscillator containing a clock pulse generator for DTMF touch dialing is characterized by the fact that the time switching device controls the time clocks of the clock pulse generator present in the digital frequency oscillator. This results in a further simplification in this special application the structure of the time switch device according to the present invention.

An expedient further development of the circuit arrangement according to the invention is characterized in that the time switch device has a counting circuit, to which the clocks are fed, and the time-defined for different ones Interruptions in the loop circuit has several separate outputs. on In this way, the same basic components of the time switch device can be used without larger ones Effort can be adapted to different operating conditions.

In the following, the circuit arrangement according to the invention will be based on a figure are described in more detail.

In the figure, only the essential parts for the invention are shown, the actual station circuit SS located between the tip and ring wires, which is shown in Series with the station circuit SS lying break contact f and the opening time of the normally closed contact f controlling time switch device ZSE.

The actual time switch ZSE consists of the Counting circuit Z with outputs 1 to 5, the start button T, the clock pulse generator TG, the gate G, the flip-flop FF, the amplifier V and the normally closed contact controlling Relay F. From the clock pulse generator TG, which contains a frequency standard, a certain given clock to the counting circuit Z. If the start button T is pressed, so the counting circuit Z is activated and the one supplied by the clock pulse generator TG Clock pulses cause the counter to run up to a certain end value. The exits 2 to 5 of the counting circuit Z each correspond to predetermined end values, while the output 1 of the counting circuit Z is activated during the first counting step. From the figure it can be seen that when running through the first counting step The flip-flop FF is set via the gate G, so that at its output A a Signal is present.

This signal is fed to the relay F via the amplifier V and initiates the opening of the normally closed contact f and thus the loop interruption. Instead of a relay, an electronic switch can of course also be used will.

When the desired count of the counting circuit Z is reached, in the figure, the counter reading assigned to output 5 becomes the flip-flop FF is reset via gate G and relay F is de-energized. So is the loop current interruption ends.

Is the subscriber station in which the circuit arrangement according to the invention Is used with a digital frequency oscillator containing a clock pulse generator equipped for DTMF touch dialing, the clock pulse generator TG is not required. In its place then steps the clock pulse generator of the digital frequency oscillator, which is marked in the figure with TG '.

3 claims 1 figure

Claims (3)

Claims (circuit arrangement for subscriber stations in telecommunications, in particular telephone systems, for the time-defined interruption of the loop current, d a -d u r c h e k e n n n z e i c h n e t that in series with the actual Station circuit (SS) a normally closed contact (f) arranged in the loop circuit (a, b) and the opening time of the normally closed contact (f) from a clock pulse generator (TG) controlled with a time switch device (ZSE) containing a frequency standard will. 2. Circuit arrangement according to claim 1 for subscriber stations with a digital frequency oscillator containing a clock pulse generator for DTMF touch dialing, d a d u r c h e k e n n n z e i c h n e t that the time switch device (ZSE) the timing of the clock pulse generator present in the digital frequency oscillator, (TG ') are supplied. 3. Circuit arrangement according to claim 1 or 2, d a -d u r c h g e k e n n n z e i c h n e t that the time switch device (ZSE) is a counting circuit (Z) to which the time clocks are supplied and which for different times Defined interruptions of the loop circuit several separate outputs (2 to 5).