DE1241494B - Circuit arrangement for telephone subscriber devices with a precious metal bridging contact in the speech circuit - Google Patents

Description

Circuit arrangement for telephone subscriber sets with a precious metal bridging contact in the speech circuit The main patent application T 24372 VIII a / 21 a3 (German Auslegeschrift 1190 513) relates to a circuit arrangement for telephone subscriber sets whose contacts in the speech circuit are bridged by a magnetically actuable - noble contact in the speech state. Thereby, it is possible to form the various iedenen located on the connection line contacts for the operation of the call circuit and the Einstellstromkreise than ordinary contacts, and only a C - 'tdelkontakt provide that prevents only peo en protected deterioration of the speech circuit by dirt.

The invention is based on such arrangements in which in the exchange When the desired participant reports, the supply voltage is reversed. This polarity reversal of the supply voltage results in proper operation of the magnetic controllable noble contact thereby exploited that as a result of the directional effect in the shunt to the speech transmitter this is now fully excited.

The invention relates to a further development of the arrangement of the main patent application with the task of monitoring the functionality of the intercom during to enable connection establishment.

This is achieved by the invention in that in a circuit arrangement for telephone subscriber sets, their contacts lying in the speaking circuit, in the speaking state be bridged by a magnetically actuated, protected noble contact, the Speech transmitter whose magnetic field, when excited, the magnetically controllable contact actuated, a directional conductor is in series with a resistor in parallel, which the speech transmitter for the current flowing in the call and setting status to a large extent short-circuits so that the contact cannot be operated, but the microphone can no matter how much power it receives that the participant can get through during the election the blow test can convince of the functionality and dialing and busy signals be perceived by the listener.

An embodiment of the invention is shown in the drawing. This shows the circuit arrangement of a telephone subscriber set and the connection of the supply voltage in the exchange. The subscriber line is connected to the terminals La and Lb. The contacts actuated by the hook switch are designated by UI and Ull. The keypad controls contacts 1 to 10. Each key also actuates an auxiliary contact 1 ' to 10'. These I-Eleven contacts are in the course of the wire La of the connection line and interrupt the circuit for microphone and speech transmitter üR during the duration of the dialing process.

The contact UI of the hook switch and the auxiliary contacts 1 ' to 10' of the dial buttons are bridged by a contact Ür, which can be closed by the magnetic field of the speech transmitter üR.

A resistor R 1 is connected upstream of the speech transmitter üR. Parallel to the windings of the voice transmitter UR is the series connection of a resistor R 2 and a directional conductor Dw. In the exchange, the wire of the subscriber line connected to terminal La is usually on the positive pole and the wire of the subscriber line connected to terminal Lb is on the negative pole the supply current source. The directional conductor Dw is permeable for this polarity. As a result, the windings of the speech transmitter ÜR are largely short-circuited. Only a weak field is generated in the speech transmitter, which is not able to operate the protected noble contact. By da 's microphone M flowing a weak current which gerade'a-usreicht that the subscriber can verify during the selection by the Blasprobe of the functioning of the vocal tract. Also, from the exchange forth transmitted aktistische sound sign for 'the No. i e of dialing and Besetztzueig supernatant are perceived by the listener H. The resistors RI and R2 are preferably voltage-dependent resistors (varistors), which have a higher resistance when the supply current is low (long line length) than when the supply current is high (short connecting line).

If the called subscriber answers after a desired connection has been established, then the contacts-wI- and wII umgeldgr. Now the - positive pole of the supply voltage source is on the wire - which is connected to -the- terminal Lb. The directional conductor DW is not permeable for this direction of the supply current. The windings of the voice transmitter üR therefore receive full current and generate a magnetic field of such strength that the protected noble contact ür is actuated and short-circuits all contacts on the connecting line.

Claims (2)

Claims: 1. Circuit arrangement for telephone subscribers whose contacts in the speech circuit are bridged in the speech state by a noble contact which can be actuated by the magnetic field of the speech transmitter, according to claim 3 of patent application T 24372 VIII a / 21 a2, d a - characterized in that the Speech transmitter (üR) a directional conductor (Dw) in series with a resistor (R 2) is parallel, which largely short-circuits the speech transmitter for the current flowing in the call and setting state, so that the contact (ür) cannot be operated, but it can the microphone (M) still receives so much supply current that the participant can convince himself of the functionality during the dialing through the blow test and dialing and busy signals are perceived by the handset (H). 2. Circuit arrangement according to Claim 1, characterized in that the upstream resistor (R 2) is designed as a voltage-dependent resistor (varistor). C Publications considered: German Patent No. 662 774.