DE1234272B - Circuit arrangement for detecting potential jumps on electrical lines, preferably connecting lines in telecommunication devices - Google Patents

Description

Circuit arrangement for detecting potential jumps on electrical Lines, preferably connecting lines in telecommunications equipment. The invention relates to a circuit arrangement for detecting potential jumps on electrical Lines, preferably connecting lines in telecommunications equipment, with over an at least two-stage transistor circuit of the potential jump a subsequent one Evaluation device influenced.

It is common to see changes in potential on electrical lines Purpose - to control the registration or to initiate further switching measures. Apart from the fact that this problem occurs with every electrical device with changing Potentials, e.g. B. Switch-on and switch-off currents on power supply lines exists, this problem occurs particularly in telecommunications and here in particular in telephony in the detection of potential jumps on the occupancy wire on.

It is already known to pass ground pulses to DC circuits of any polarity applied to the switching electrodes on the base side To lead switching transistor to connecting terminals, optionally via a contact bracket can be connected to a common ground terminal and each of which is free Terminal can be switched through to the DC circuit to be connected.

It is here for everyone to be influenced by the grounding impulses DC circuit requires an evaluation element in the form of a relay. For the from the evaluation to be optionally excluded direct current circuit of certain polarity a closed circuit is closed via the contact clip.

A transistor is also known for detecting potential jumps from the conductive to the non-conductive state or vice versa, which in turn controls another transistor in the pass band, so that the over the second transistor flowing current brings an evaluation device to respond. Disadvantage of such Arrangements is, however, that only potential jumps in one direction are found can be.

The object of the invention is to use a single evaluation device to process both positive and negative potential jumps. This is because of this achieves that depending on the direction of the potential jump to be evaluated at the input of the circuit arrangement, the base of the control transistor by means of a switching device can be connected to the emitter or collector of the pre-stage transistor, the applied to the emitter of the control transistor voltage according to their value between the voltage present at the emitter resistor of the pre-stage transistor and the supply voltage lies.

With a simple switchover, combined with a corresponding one Choice of pre-tensioning can therefore be advantageous without additional intervention both a positive and a negative potential jump in the evaluation device be evaluated.

The invention is explained in more detail with reference to the figure using an example.

The switching element S1 ... S5 shown in the figure can consist of a manually operated switch, a relay or an electronic switching device. If the operating point of the transistor T1 is selected accordingly, the switching means labeled S2 ... S5 may be omitted.

When testing a positive voltage jump at the input E of the circuit arrangement, the switching means S 1 ... S 5 are switched through in position 1. The capacitor C is charged and the transistor T1 is controlled in its pass band. If a positive potential jump now reaches the input E of the circuit arrangement, the capacitor is recharged and the transistor T1 is blocked for the duration of the recharging. Thus, via .das switching means S1, a negative potential is applied to the base of transistor T2, whereby evaluation element A, e.g. B. a relay is made to respond. The size of the necessary jump in potential can be determined by setting the negative voltage U3 in relation to the voltage across the resistor R 8. A precise setting of this voltage threshold is also possible by selecting a corresponding Zener diode G2.

To register negative potential jumps, the switching means are switched to position 2. In this switching state, both transistors are blocked in the rest position. If a negative potential jump reaches the input E of the circuit arrangement in the manner described above, the capacitor C is recharged and the transistor T1 is controlled in its pass band. Since the base of the transistor T 2 is connected to the emitter of the precursor transistor T 1 , the transistor T 2 is opened when the emitter-collector path of the transistor T1 is switched on.

Claims (2)

Claims: 1. Circuit arrangement for detecting potential jumps on electrical lines, preferably connecting lines in telecommunications equipment, wherein the potential jump via an at least two-stage transistor circuit influencing subsequent evaluation device, characterized in that in dependence on the direction of the potential jump to be evaluated at the input (E) of the circuit arrangement the base of the control transistor (T2) by means of switching device (S1) to the emitter or collector of the pre-stage transistor (T1) can be switched on, with the at the emitter of the pre-stage transistor applied voltage (U2) according to its value between the the emitter resistor (R 6) of the pre-stage transistor applied voltage (U1) and the supply voltage. 2. Circuit arrangement according to claim 1, characterized in that further switching devices (S2 ... SS) are provided with which the bias voltages for determining the operating points of the transistors (T1, T2) are switched. Documents considered: German Auslegeschrift No. 1131751.