DE1034701B - Circuit arrangement for subscriber stations in telecommunications, especially telephone systems, with keypad selection - Google Patents

Description

GERMAN

LIBRARY OF THE GERMAN PATE OFFICE

In telecommunications, in particular telephone systems, it is known to use tone frequency generators at subscriber stations provide their different transmission frequencies to identify the respective desired subscriber to serve.

Subscriber stations are also known in which amplifier switching means, e.g. B. tubes or transistors, serve to amplify the microphone currents.

To simplify such stations, it has been proposed to amplify the microphone streams Serving amplifier can be switched on by pressing a button and according to the respective necessary transmission frequency to bring selectable feedback elements to self-excitation. With such Subscriber stations, however, the amplifier switching means are always switched on, regardless of whether they are required for an established connection or not. For example, if a connection is made within a PBX or a public office set up over a short distance, so is not necessary an amplification of the microphone currents; However, the amplifier switching means are also switched on in this case, are subject to wear and tear and represent an additional power consumption. On the other hand, brings an amplification of the microphone streams has the disadvantage that the more recorded in the office Speech currents conducted via lines and switching means that are specially protected against crosstalk or crosstalk.

The present invention relates to a circuit arrangement for subscriber stations in telecommunications, in particular telephone systems, with keypad selection, in which when keys of a subscriber station are pressed the latter assigned generators to the actuated keys corresponding code characters in the form emit at different frequencies, and aims to eliminate the disadvantages of the described arrangements to avoid. This is achieved by assigning a switching device to the subscriber station is the switching means serving to generate the code characters as an amplifier in the incoming direction um-, one switched on during the transmission of code characters to the secondary winding of the fork transformer Handset of the subscriber station via a secondary winding for generating code characters serving voice coils to the output of the amplifier and at the same time said winding of the Connect the fork transmitter to the input of the amplifier.

By switching over the switching means used to generate the code characters as amplifiers in Incoming direction is an overuse of the facilities in the office with regard to secondary or Crosstalk avoided in any case. There is also circuitry

for subscriber stations in telecommunications,

in particular telephone systems,

with keyboard selection

Applicant:
Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dr. phil. Josef Schnurr, Munich,
has been named as the inventor

but also given the possibility of using a switching device, the amplifier switching means only to be taken into use if, for example, by the participant when occurring Disturbances of communication are deemed necessary, so that they only wear out in these cases and represent an additional electricity consumer.

In order to give the participant the possibility of the incoming characters during the voting breaks (e.g. dialing signals, busy signals or the like), the listener at the subscriber station is not directly with the before actuation of the switching device for sending the code characters and after actuation of the Switching device connected as an amplifier in the incoming direction serving switching means. He is rather, it is connected to the secondary winding of the fork transformer in the rest position of the switching device, so that the participant during the election without actuating the switching device the incoming Can eavesdrop on characters. These signs are generally switched on in the office with a level which does not require reinforcement.

In contrast, there is another known arrangement for car telephony, in which to transmit Callsign an amplifier which is used to amplify the microphone currents by pressing a button Switchable feedback elements is brought to self-excitation. In this known arrangement an additional one is used to receive incoming characters (e.g. dialing signals, busy signals or the like)

809 578/156

Expended amplifier with a .invention Arrangement is saved.

In order to continue to make the switching of the subscriber station particularly simple, the fork transmitter is used as an input transmitter for the amplifier after actuation of the switching device and the coils located in the resonant circuit for generating the code characters are also used as output transmitters. This enables a very compact design, so that an arrangement according to the invention can be accommodated in a normal telephone housing. \

An exemplary embodiment is shown in the drawing in which the switching means used to generate the code characters act as an amplifier for the conversation can be switched in the incoming direction.

A transistor is used as switching means for generating the code characters and for amplification is known to be fed via the subscriber line. As contacts of the switching device normal key contacts can be used. However, to ensure safe and trouble-free operation To ensure the device, it is advisable to use protective tube contacts, which are then connected to a common permanent magnets are operated. When combining the switching device with a The protective tube contacts do not bring any additional buttons that are already present or with the hook switch mechanical load on the mechanical component to be moved for their actuation.

For the sake of simplicity, it is assumed for the exemplary embodiment shown in the drawing that the contacts of the switching device by a special switch, a special button or the like., independently of the hook switch or other already existing switching means.

To set up a connection, the subscriber lifts his receiver, whereby the contacts of the hook switch IAm, 2 hu are actuated; the subscriber loop is closed at contact 2Am. Upon actuation of one of the selection buttons on the subscriber station of this key associated contact 1 is 1 .. and NG and all of the keys common contact 5 1 is closed and the contact 4 1 is opened. At contact 4 1 , microphone M and receiver // are switched off from subscriber line a, b and at contact 5 1 the frequency generator used to generate the code characters is connected to the subscriber line. As already explained, a transistor Tr is used as the switching means for generating the code characters. The oscillating circuit of the generator consists of the inductances go LjI to Ls 3 and a capacitance Ks. The key contacts il to iO are in a single contact in the figure for the sake of simplicity united.

By means of the contacts, either different capacitances Ks or different inductances Ls 3 can be switched into the resonant circuit in order to generate different frequencies. It is also conceivable that different capacitances Ks with different inductances Ls 3 are connected together in different combinations. So z. B. three different inductors with four capacitances are combined in such a way that twelve frequencies arise.

The evaluation of the different frequencies given by pressing a key can be done in the office on filters matched to these frequencies and relays connected downstream.

After the connection has been established, the calling subscriber can operate the switching device and thus the contacts 6m to 15 «. The transistor 73 is thereby switched over as an amplifier in the incoming direction. At the contacts 6 m, 1Ou , the subscriber's handset H is switched off by the secondary winding '(P3 of the fork transformer Gl, G2, (73.''Ah the contacts Tu, 9m, the secondary winding G 3 of the fork transformer between the coupling capacitors K 2 and the base of the transistor Tr and thus connected to the input of the amplifier. The output of the amplifier is formed by the resonant circuit coils Ls2 and Ls 3 in connection with the secondary winding L4, to which the receiver H is connected via the contact 11M. At the contacts 13m and 12m the coil Lsi is switched off or bridged. The amplifier is connected to the α wire via the 15 m contact.

The arrangement shown in the drawing is intended per se for ungrounded subscriber stations; the transistor is therefore asymmetrically coupled to the subscriber line for operation as a generator. At subscriber sites with earth, z. B. PBXs or service stations, a symmetrical operation of the transistor Tr as a generator is quite conceivable.

Claims (2)

Patent claims: 1. Circuit arrangement for subscriber stations in telecommunications, in particular telephone systems, with keyboard selection, in which, when keys of a subscriber station are pressed, the generators assigned to the latter send out corresponding code characters in the form of different frequencies to the actuated keys, characterized in that the subscriber station has a switching device (contacts 6 m up to 15 m), which switch the switching means (Tr) used to generate the code characters as an amplifier in the incoming direction, a receiver (H) of the subscriber station connected via a secondary winding while the code characters are being transmitted to the secondary winding (G 3) of the fork transmitter (L4) of voice coils (Li 1, Ls 2, Ls 3) serving to generate code characters to the output of the amplifier and at the same time the said winding of the fork transformer (G3) to the input of the amplifier. 2. Circuit arrangement according to claim 1, characterized in that as contacts of the switching device (Contacts 6m to 15m) Protective tube contacts can be used, which are operated jointly by a permanent magnet. Considered publications:
German Patent No. 622,343;
German patent application ρ 36984 VIII a / 21 a ² D; "Radio Mentor", issue 7, 1950, p. 351. 1 sheet of drawings 1 809 578/156 7.58