DE1199827B - Circuit arrangement for the supply of the subscriber stations in telecommunication systems, especially telephone systems - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H04m

German KL: 21 a3 - 29/01

Number: 1199 827

File number: T 26230 VIII a / 21 a3

Filing date: May 21, 1964

Opening day: September 2, 1965

The invention relates to a circuit arrangement for supplying the subscriber stations in telecommunications, in particular telephone systems, in which the supply current from the office battery by means of a symmetrical constructed feed element is fed to the two speech wires s of the subscriber line.

In telephone systems, the microphones and dialing devices of the subscriber stations are generally used fed from the battery of the associated exchange. For this purpose, the speech arteries the subscriber line in the speech state in the connection devices of the office via so-called Feed members connected to the office battery. Since the transmission of both the supply current and also the speech streams takes place over the same line, must on the one hand, in order not to the feed stream to weaken, the DC resistance of the supply element can be kept low, but on the other hand is not only negligible attenuation, but also Also a perfect symmetry of the transmission path is important, because every asymmetry is a disruptive influence through couplings and equalizing currents. The symmetry is just if the electrical properties, especially those of the feed element for the two speech wires are the same, d. H. when the ohmic, inductive and capacitive resistances match.

It is known to use chokes as a feed link between the speech wires and the poles of the official battery to switch the highest possible inductive but the lowest possible ohmic resistance. These will often designed as the windings of a relay. Especially for keeping interference voltages away At a lower frequency, this results in very large components, with which the contradicting one nevertheless occurs Requirements can only be partially met.

In contrast, the invention shows a circuit arrangement which eliminates the disadvantages mentioned by that the feed member consists of two mutually complementary transistors, the emitter electrode Via resistors one pole of the official battery and its collector electrodes each are connected to a speech wire, and that the operating points of the two transistors in the speech state the connected subscriber station by bias voltages connected to their base electrodes are kept in the linear range of their characteristics.

It is known that with transistors - just as with electron tubes - for each operating point in the linear range of the characteristic field between the circuit arrangement for the supply of the
Subscriber positions in telecommunications, in particular
Telephone systems

Applicant:

Telefunken

Patentverwertungsgesellschaft mb H.,
Ulm / Danube, Elisabethenstr. 3

Named as inventor:

Norbert Budnik, Backnang (Württ.)

static and dynamic internal resistance can be distinguished. The static internal resistance determines the direct current flowing in the circuit of the emitter-collector path while the much higher dynamic internal resistance is decisive for current changes.

By inserting the emitter-collector path of a transistor into one of, for example, a Battery and a subscriber station in the speech state formed circuit is with the help of the operating point setting of the transistor impressed a direct current, while the resistance of the transistor for the alternating currents flowing in the circuit is very high. This is highly dynamic Internal resistance in the occurring range independent of frequency.

The invention is explained in more detail using an exemplary embodiment. In the circuit diagram, the subscriber station TIn can be connected via a switching network EKF to a connection set which is not described in detail and which contains the feed element. In the supply element, the speech wire α is connected to the negative pole - U _{B of} the office battery via the series connection of the resistor R 1, the collector-emitter path of the transistor TsI and the resistor R 4 and the speech wire b via the series connection of the resistor R 2, the collector-emitter path of the transistor Ts 2 and the resistor R 5 connected to the positive pole + U _{B of} the office battery. The resistors R 1 and R 2 are only protective resistors and are used to limit the current in the event of interference voltage peaks. The transistor Ts 1 is of the npn type, the transistor Ts 2 of the pnp type. The resistors R 4 and R 5 are in the emitter leads, so they are common to the emitter-collector and the emitter-base circuit,

509 659/99

They therefore contribute to increasing the dynamic resistance of the corresponding emitter-collector path by countercoupling the current. A voltage drop occurs across them when the current is flowing. Therefore, suitable control potentials must be applied to the base electrodes of the transistors TsI and Ts 2 in order to set a usable operating point. This is done by the potentials [71 or U 3, for which the rectifier paths GrI or Gr 2 are in the reverse direction. The rectifier sections Gr 1 and Gr 2 are silicon diodes, which have approximately the same temperature response of the threshold voltage as the base-emitter diodes of the silicon transistors TsI and Ts 2 and therefore the operating point of the transistors TsI and Ts 2 in a known manner stabilize on temperature fluctuations. The base current is fed into both transistors TsI and Ts 2 via the resistor R 3, while the rectifiers GrI and Gr 2 ensure the temperature-dependent behavior of the base bias voltage required for stabilization.

If no subscriber TIn is connected via the coupling network EKF or if the connected subscriber has hung up his handset and thereby interrupted the loop circuit, the transistors saturate, and only voltage drops corresponding to the base current occur at the resistors R 4 and RS Block rectifier sections GrI and Gr2.

The dial pulses and other switching indicators can be determined as a result of their voltage drop across the resistors R 4 and / or R 5 with the aid of an evaluation device M.

The rectifier sections Gr3, Gr4 and Gr5 are protective diodes to divert interference voltage peaks that could come from the line to the collector electrodes of the transistors TsI and Ts 2.

It is common in switching systems to decouple the direct current paths of the calling and called subscriber station. Here the decoupling is effected by the local line transformer OLÜ . The voltage U 2 connected to the inner winding end of the left-hand transformer winding absorbs the unavoidable differential current of the transistors TsI and Ts 2 and keeps the voice wire b at a fixed potential. Otherwise one or the other transistor could be saturated in the speech state. So

The insertion loss of the feed element described is so small that it is not absolutely necessary to connect the transistors TsI and Ts 2 to the speech cores α and b at the same point; the connection points can also be spatially apart without a disruptive asymmetry occurring.

Claims (5)

Patent claims: 1. Circuit arrangement for feeding the subscriber stations in telecommunication systems, in particular telephone systems, in which the feed current from the office battery is fed to the two speech wires of the subscriber line by means of a symmetrically constructed feed element, characterized in that the feed element consists of two mutually complementary transistors (TsI, Ts2 ) , whose emitter electrodes are connected via resistors (R4, R5) to one pole of the office battery (- U _B , + U _B ) and whose collector electrodes are each connected to a voice wire (a, b) , and that the working points of the two Transistors (TsI, Ts 2) in the speech state of the connected subscriber station (TIn) are kept in the linear range of their characteristic curves by bias voltages (U 1, U 3) connected to their base electrodes. 2. Circuit arrangement according to claim 1, characterized in that the resistors (R4, R5) switched on in the emitter leads of the transistors (TsI, Ts 2) cause an increase in their dynamic internal resistance through negative current feedback. 3. A circuit arrangement according to claims 1 and 2, characterized in that the position of the operating points of the two transistors (TSI, Ts 2) in a known manner by means of a respective switched rectifier section (GrI in the Basiszujeitungen of the transistors (TSI, Ts 2) , Gr 2) is stabilized against temperature influences. 4. Circuit arrangement according to claims 1 and 2, characterized in that the evaluation of the dialing pulses and switching indicators on the one or the two in each case between the emitter electrode of a transistor (TsI or Ts 2) and the corresponding pole (- U _B or + U _B ) switched resistors (R 4 or R 5) takes place. 5. Circuit arrangement according to claims 1 and 2, characterized in that different values of the collector currents of the two transistors (TsI, Ts 2) are collected by applying a fixed reference potential (E / 2) to the inner end of a winding of a local line transformer (OLÜ) . 1 sheet of drawings 509 659/99 8.65 © Bundesdruckerei Berlin