DE520801C - Device for limiting the currents in a transmission line - Google Patents

Description

The invention relates to transmission systems and more particularly relates to a method and to means for regulating the strength of the currents to be transmitted.

The invention is particularly applicable to transmission systems employing a microphone connect to a remote wireless transmitter. Such facilities that

ίο use the existing telephone lines, may take into account the magnetic cores of the Pupin coils connected in the line no excessive currents occur, otherwise the magnetic conditions of the Change the means of exercise. On the other hand, however, the currents at the end of the line must be true to shape those at the beginning of the line.

The object of the invention is the automatic limitation of the strength of the currents on the line, but without changing its strength on the receiving station.

The invention consists essentially in the following: When the currents on the transmitting station exceed a predetermined certain value, their oscillations are automatically converted into direct currents, the are suitable for transmission over an ordinary telegraph line. The DC pulses automatically weaken the currents sent into the line at the transmitting station. Be at the same time these direct current pulses are sent to the receiving station via a telegraph line, where they automatically cause the currents to increase at the end of the line and thereby cancel their reduction caused on the transmitting station.

The invention is explained in detail using the illustration. The figure shows an exemplary embodiment of a telephone transmission system in which, according to the invention, the strength of the telephone currents is regulated which are transmitted from a microphone to a remote wireless transmitting station. The currents of a microphone M at station A go through a potentiometer P and an amplifier 1 to a compensation circuit 2. This has a fixed resistor 25. Regulation is effected by changing the equilibrium of the circuit 2 by changing the impedance of the output circuit the vacuum tube V ₂ , which will be discussed further below. From the equalization circuit 2, the currents are fed via an amplifier 3 and the telephone line L to a second equalization circuit 4 with a resistor 26 on the receiving station B. That

The balance of this circuit 4 is changed according to the arrangement x 2 by changing the impedance of the output circuit of the vacuum tube V ₃ . From the compensation circuit 4, the currents pass to the amplifier S and to the wireless transmitting station. From points 6 and 7 of the line L branches off a line L ₁ , which is inductively coupled by the coils 8 to the grid circle of the vacuum tube V-L, the latter being used as an indicator. In the grid circle of the tube is a battery 27, the voltage of which is selected so that normally only a weak anode current flows in the tube. The vacuum tube allows a direct current to flow in its anode circuit when an alternating voltage is applied to its grid. The indicator of the invention differs from the usual ao Ausrührungsform in that a polarized relay R _{1 is} used in the anode circuit instead of the usual MiUiamperemeter, which, as explained in more detail below, reacts sluggishly. The polarized relay R ₁ has three windings 9, i and 11. The winding 9 serves as a magnetizing winding and is fed via a resistor 12 from a local battery. In the exemplary embodiment, the anode battery of the tube V _{1 is also used} for this purpose. The winding id is in the anode circuit of the tube V ₁ and serves as the main working winding of the relay. The winding 11 serves as an auxiliary holding winding and is operated by the batteries connected to the contacts of the relay, as shown in the drawing. This winding 11 is connected on the one hand to the armature of the relay and on the other hand via resistor 13 and capacitance 14 to earth and connects the relay armature to one of the contacts M or S for a period depending on the value of the resistor 13 and the capacitance 14 In this way the buzzing of the armature in time with the speech currents is prevented, and the relay is made sufficiently slow to generate pulses T suitable for transmission over an ordinary telegraph line.

The windings of the two other polarized relays R ₂ and R _{3 are} connected to the armature of the relay R _1. As will be seen later from the description of the mode of operation of the relay, it regulates the change in the transmission value at the transmitting station by changing the impedance of the anode circuit of the tube. The relay R _z , which is in series with the relay R _2, transmits the controlling direct current impulses via the telegraph line to the receiving station B, where these impulses compensate for the switching dimensions that have occurred at the sending station by changing _{the impedance value of the output circuit of the pipes V 3.}

The arrangement according to the invention works in the following way: For example, the value of the resistor 25 is _{assumed to be 15,000 ohms, that of the impedance of the tube V 3 is} assumed to be 6000 to 15,000 ohms. Likewise, at the receiving station, the value of the resistor 26 is set at 5100 ohms, that of the variable impedance of the tube V ₃ at 6000 to 15,000. When the anchors of the relays / ?! and R _{2 are} at their empty contacts S, the impedance of the tube V ₂ at the end of the equalization circuit 2 opposite the resistor 25 has the value 6000 ohms, i.e. a much lower ohmic value than the equalization resistor 25. As a result of this difference in resistances (15000 to 6000 Ohm) in the bridge circuit 2, by far the largest part of the currents reaches the connecting line L, so that the transmission value of the compensation circuit can be described as high or the transmission losses as low.

When the level of the telephone currents at the beginning of the telephone line exceeds a predetermined value, the peaks of these currents are automatically converted into direct currents in the indicator V. As a result, the anode current in the indicator increases enough to throw the armature of the relay / ^ from the empty contact S to the normally open contact M. This process also causes the armature of the relays R ₂ and R _s to be moved to their normally open contacts M. By moving the armature of the relay R ₂ to its contact M , the negative pole of the battery 15 is connected to the grid circle of the tube V ₂ . The current of the battery 15 flows through the filter 16 and the resistor 17, which creates a negative voltage on the capacitor 18. The growth of the negative potential to the grid of the tube V ₂ increases the impedance of the anode circuit of this tube, so that the impedance of this circuit is brought out closer to the equilibrium value of 15, 000 ohms of resistance 25th This results in an increase in the transmission losses in the compensation circuit 2, namely until the level of the telephone currents at the beginning of the line has become low enough _{to cause the relay / ^ 1} in the indicator circuit to drop out. The armature of the relay ^ ₁ returns to its empty contact S, the capacitor 18 is discharged through the resistor 19. The level of the telephone currents then rises again until the relays R ₁ and R ₂ respond again, whereby the process described above is repeated. It's him-

It can be seen that the operation of the relay R ₁ in response to the peaks of the speech currents produces an average voltage value across the capacitor 18 of such magnitude that the correct level is maintained at the beginning of the line.

As explained, the relay R ₁ also acts on the relay R ₃ . When the anchor of the latter is on its working contact

ίο is located, direct current pulses are transmitted over the telegraph line T to the 'relay R ₁ on the receiving station B. This relay acts on the circuits of the vacuum tube Vs in the same way as the relay /? » the transmitting station A to the currents of the tube V ₂ . When the armature of the relay R _{1 is switched} to its normally open contact in accordance with the current impulses transmitted over the telegraph line, the negative pole of the battery 20 is connected to the grid of the tube V ₃ . The current from the battery 20 flows through the filter 21 and the resistor 22 and creates a negative voltage on the capacitor 23. The increase in the negative voltage on the grid of the tube V ₃ increases the impedance of the anode circuit of the tube from 6000 ohms to approximately 15,000 ohms. Since, as mentioned above, the value of the fixed resistor 26 in the compensation circuit of the receiving station is 5100 ohms, the increase in the anode impedance of the tube V ₃ , depending on the action of the relay R _{1, increases} the inequality of the compensation circuit. As a result, the transmission loss within the compensation circuit is reduced and the current at the output of the line is increased.

From the above description it can be seen that the invention provides for the excessive Increase of the currents on the station yl automatically by decreasing the To prevent currents at the beginning of the line and by increasing the currents at the end of the line at the receiving station automatically balance.

The invention is not limited to the use of the compensation circuits described limited, and other types of devices can be used for the same purpose will.

Claims (4)

Patent claims: I. Device for limiting the currents in a transmission line, in particular those for influencing a wireless transmitter, characterized in that at both ends of the connecting line Transmission devices (e.g. bridge or equalization circuits) are arranged, the transmission value of which are in opposite directions is changed via an auxiliary line (e.g. a telegraph line) in such a way that a certain current value is not exceeded in the connection line. 2. Device according to claim 1, characterized in that the transmission devices consist of equalizing circuits (2, 4), in one branch of which fixed resistors (25, 26) of mutually different sizes are switched on and the conductivity in the other branches Modified vacuum tubes (V ₂ , V ₃ ) are changed in their imbalance in such a way that when the current to be transmitted increases, the equalization circuit (2) at the beginning of the line causes greater and the equalization circuit (4) at the end of the line causes lower transmission losses. 3. Device according to claim 1 and 2, characterized in that at the beginning of the transmission line (L) there is a switching device parallel to it, which consists of a vacuum tube rectifying the speech currents (V ₁ ) and a preferably polarized relay (^ ₁ ) which is insensitive to the fluctuations in the speech currents that occur in the rhythm of its influence and, via the auxiliary line (T) with the interposition of two relays (R ₂ and R ₃ ), the conductivity of the vacuum tubes changing the resistance compensation of the compensation circuits (e.g. by shifting their grid bias) changes. 4. Device according to claim 2 and 3, characterized in that the fixed Resistance (25) in the equalization circuit at the beginning of the transmission line is greater than that in the compensation circuit (26) located at the end of the line, and that when it grows the currents to be transmitted the tube impedance value at the beginning of the line approaches the value of the fixed resistance, while the tube impedance value at the end of the line differs from the value of the fixed resistance removed. For this purpose ι sheet of drawings