FI60330C - COVERAGE FOR THE CONSTRUCTION OF TELEGRAPHIC CONNECTORS FOR VAEXELSTROEMSOEVERFOERINGSANORDNINGEN OCH - Google Patents

Description

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(41) Published by Mktl - Bllvit offuntlif 06.09.7l

Patent and Registration Office .... , . _. ^. , (44) Date of issue and date of issue. -

Patent- och registerstyrelsen 'AmOkin uttajd oeh utl. * Krift «n publkend 31.08.81 (32) (33) (31) Pyydetty ttuoikuus —Begird prior 05.03.73

Federal Republic of Germany-Förbundsrepubliken

Tyskland (DE) P 23109 ^ 0.2 Proven

Styrkt (71) Siemens Aktiengesellschaft, Berlin / Miinchen, DE; Wittelsbacherplatz 2, D-8000 Munchen 2, Federal Republic of Germany-Förbundsrepubliken Germany (72) Ernst Schuhbauer, Munich, Fritz Giebler, Munich, Peter Rath, Munich, Federal Republic of Germany-Förbundsrepubliken Germany (DE) (5 * 0 Switching device for connecting telegraph subscribers to AC transmission and transmission equipment - Kopplingsanordning för anslutning av tele-grafabonnenter account växelströmsöverföringsanordningen och förmedlings-anläggningar

The invention relates to a switching device according to the preamble of claim 1 for connecting telegraph subscribers to alternating current transmission devices and transmission devices via wires of different qualities and lengths with direct current keying.

As is known, DC transmission technology with a high transmission delay is used in local telecommunication and data processing networks. Subscribers are connected with two-way four-wire dual power lines (eg -60V, -20mA) or semi-bidirectional two-wire single-current cables (eg 120V, 40mA) to transmission plants or AC transmission equipment. Only in special cases are subscribers connected by two-way four-wire single-current cables (eg 120V, * 40mA). Subscribers are connected to the relay by single-current-dual-current converter connections. Figure 1 shows such a converter connection in Telecommunications. The teletypewriter sk, EM is connected to the converter circuit by a line L. The transfer of characters from the exchange to the subscriber takes place with a short-circuit key. Data conversion takes place with two polarized electrification relays - receiving relay A and transmitting relay B.

Relay U acts to change the polarity of the subscriber loop and to connect the holding circuit 60330 si (holding resistor RH), which prevents reflections. With the line replenishment resistor RL, the line current must be set on a per-subscriber basis, the equalization resistor RN acting to smooth the reception distortion as little as possible.

With this DC electrification, a high transmission voltage has many advantages: the receiver is fed directly from the transmission center.

The connections required by the subscriber are therefore simple and inexpensive. The connections made in the center are also simple and cheap. In addition, the costs of the center can still be reduced through centralization. The high transmission voltage brings with it high certainty against interference (modulation distortions, resp. Faults) and insensitivity to contact overshoot resistors (e.g., when subscriber switching fields are centralized in a control panel or concentrators). Finally, this known technique requires only simple methods and inexpensive, sturdy drive devices.

However, a large power loss per subscriber in the exchange is disadvantageous. This is annoying due to the high resistance of the line replenishment, especially in the case of short cable lengths and short-circuit and earth-fault cases, and requires measures to combat the risk of fire.

Because subscribers are connected to the exchange via different and different length wires, a wire replenishment resistor must be set manually for each subscriber. In four-wire operation, the setting of two wire replenishment resistors is necessary. In addition, the distortion compensation required in two-wire operation in each converter connection makes it necessary to adjust the compensation resistance manually per subscriber. High transmission voltage leads to high interference voltages in adjacent lines due to crosstalk. This drawback means a great deal, because it is expected that the requirements for the interference voltage as data traffic increases even at lower transmission rates (50 Bd).

However, a DC transmission technology with the lowest transmission voltage has now become known (German Patent Publication 1,251,798) for local loops, which greatly avoids the above-mentioned drawbacks of the technology described above. However, this technique requires an indirect way of operating remote typewriters and thus requires a relatively large amount of instrumentation at the subscribers and at the exchange. However, for high speeds, this transmission technology at low transmission voltages may be necessary. At lower speeds, 3,60330 up to 200 Bd, however, another economical solution is sought. This speed class already includes a very large proportion of subscribers worldwide. For these subscribers, the change should be as simple and inexpensive to implement as possible.

German application 19 11 252 already discloses another connection in which, except in extreme cases, a state-specific distortion compensation by changing the compensating resistance is unnecessary. Thus, when using such a converter connection, one of the disadvantages of the known connection technology has already been eliminated.

The object of the invention is to provide an interface connection for telegraph subscribers which preserves the advantages of known connections and avoids the disadvantages of known connections.

This object is solved according to the invention and it is characteristic of the invention that each connecting line is provided with its own unearthed power supply and that in each subscriber connection connection an electronic device is connected to the electrification line to smooth the keyed DC ramps sent to the subscriber points.

With this switching device, the following results can be achieved: automatic control of the line current makes it possible to avoid the individual setting of the line replenishment resistance and to reduce the power losses of the subscriber lines in the short-circuit and earth-fault in the exchange. The power dissipation is limited to the maximum operating value. A customer-specific, unearthed power supply is also essential. This achieves, just like with a symmetry choke at the transmission-side input of the subscriber line, but more efficiently and with less intensity, that the characteristics of a given line - especially its crosstalk attenuation - are not distorted by an asymmetrical connection. This has the advantages of almost non-existent distortions, easier compliance with interference voltage requirements and simpler measures against external interference voltages (e.g. the effect of lightning or high current). In order to meet the interference voltage requirement, in addition to the symmetrical operation of the subscriber line, an electronic smoothing circuit is reserved for cutting off the higher frequency parts of the transmitted signal. If conventional simple low-pass filters were used, the required cut would lead to an unauthorized increase in electrification distortion i 4 60330. The electronic switching elements make it possible to form signal curves which guarantee optimal transmission with the lowest possible interference voltage. Electronic smoothing circuits are simply feasible and have the small space requirement as an added advantage at low cost.

When switching to a new connection technology, its compatibility with the known technology must be taken into account. Interoperability with conventional technology is possible for changes in air or small connections. in direct teletypewriter mode. It also follows that the same simple measurement technique as in the known connection technique can be used.

Moreover, it is possible to use the measures proposed by the invention in hitherto known instruments and devices not only in combination with the hitherto known technology, but also independently, to improve certain properties thereof. Finally, the use of the measures proposed according to the invention is not limited to transmission systems using a high transmission voltage. Properly modified, these measures are also advantageous in new systems using a medium or low transmission voltage.

Within the scope of the invention, it is also possible to make an automatic control connection for continuous current or voltage control. The advantage of this embodiment is that the cost is relatively low and there is no difficulty in balancing the output current.

Instead, the construction of automatic control circuits as a key control has the advantage that the power loss is not only reduced in the event of a short circuit and an earth fault, but also in normal operation.

If the control circuit is constructed in such a way that the control is fast compared to the baud rate, it is possible to save power losses in the holding resistance of the converter circuit. Due to the quick adjustment, practically any value can be assigned to the holding resistor. If the value is zero, it does not consume any power.

In addition, connections that only work with a single-current connection cable can save a switching distance that is otherwise bridged by the holding resistor. This means a considerable reduction, especially in electronic connections. In addition to this, there is an improvement in the transmission characteristics of short wires, because due to the omission of the wire replenishment resistance, the wire is recharged faster.

5,60330

With the switching device according to the invention, several functions can be implemented with connections that are very similar or contain the same or similar components and connections. Therefore, in a preferred embodiment of the invention, several functions are performed on the same components. In this way, space and costs can be saved.

Other details of the invention will be explained with reference to the embodiments shown in the drawings. There is shown in Figure 2 converter circuit for changing the two-wire-one stream of four-wire dual power use is ungrounded power supply keyed voltage control, Fig for constant current control 3 periaatekytkemän space-jaliitäntäkytkennässä, Fig principle of the coupling for the continuous voltage control of the subscriber aliitäntäkytkennässä, Figure 5 the principle of coupling to the formula in the tested current within the subscriber aliitäntäj ohdossa, Figure 6 the principle of coupling to the formula in ungrounded muuttaja- for connection with electronic wire supplementation and Fig. 7 shows the connection technical structure of the connection according to Fig. 6.

Fig. 2 shows a two-wire-single-current / four-wire-dual-current converter connection with a short-circuit keying or if the keying circuit drawn with broken lines is arranged - the so-called as well as with the key in the exchange and the interruption key at the subscriber. Down the left in the drawing is detected electronic relay B which is controlled by a four-wire dual-stream-side terminals a3> b3. In parallel with relay B, a relay L is required for selection associations in series with the electronic deceleration circuit LZ for the development and modification of the transmission criteria. This time element of the relay L is operated with a grounded supply voltage and is therefore connected to the AC-electrification center, because the line and the subscriber side according to the invention use an unearthed power supply. The upper left drawing shows the electronic contacts ak1 and ak2 used by the electronic relay A, through which the telegraphs, provided with the desired voltage and internal resistance values, are passed on to the AC electrification transmitter or exchange. Instead of a mechanical changeover switch, separate electronic contacts are then provided, because the electronic changeover switch cannot be implemented by means of a transistor. A series connection is also connected to the line between the contacts ak1, 6 60330 ak2 and the terminal a2 in the selection connections also from the necessary relay R and the electronic deceleration connection RZ for the development and modification of the transmission criteria. Through terminals a2, b2, the double-current signals generated by relay A are applied to the exchange, i.e., to the AC electrification transmitter. A subscriber line is connected to the terminals ai, bl in the right drawing. An electronic switch bk2 is connected between the conductors a1 and b1 via the contact II, which connects the current source SV of the electrification conductor b1 to the positive potential + U. With the help of the electronic contact bkl, the telegraph loop can be grounded in the direction of the subscriber for electrification - possibly via an additional connection Z. If contact bkl is closed, current holds from terminal + U through contact II, staple resistor RH, contact rll and contact bkl to the converter connection US to terminal -U. An electronic connection EA is connected to the electrification conductor bl for smoothing the pulse wave. In order to reduce the interference voltage, it is necessary to cut off the highest frequency parts of the transmitted signal. Due to the relatively strict requirements for the permissible interference voltages, this cut-off must be so steep that the use of standard simple low-pass filters already achieves the limits allowed for undistorted transmission. When using electronic means, it is possible to form curve shapes for the signal, which with a minimum interference voltage ensures optimal transmission. Active low-pass filters can be used. Such connections are, for example, simple to implement with emitter followers whose base is connected to the RC elements and have the advantage not only of low costs but also of low space requirements. Corresponding electronic limit connections can also be arranged before the electrification connection. As the converter circuit US, a circuit that avoids subscriber-specific distortion smoothing can be used, using the principle of RC keying circuit. Such a keying is already known from German application 1 911 252.

According to the invention, manual adjustment of the line replenishment resistance by means of automatic line current control is now avoided, and the power losses can also be limited to the maximum operating value in the event of a short circuit. An additional advantage of the automatic line current setting is - when built as a quick control - the possibility of saving power losses in the stapling resistance of the converter circuits. Based on the quick adjustment, the holding resistor can have virtually any value of 7,60330, i.e. also zero, and then no power is consumed. In addition, in connections that only operate on single current in the connecting line, the connection path whose braking resistor is otherwise bridged can be omitted. This causes a considerable reduction, especially in electronic connections. In the circuit according to Fig. 1, the point between the line replenishment resistor RL and the transmission contact b is then connected to the terminal + TB via the electronic control circuit and the connection between the transmission contact b and the terminal + TB as well as the holding resistor RH are omitted. If now the transmission contact b is open, i.e. the line L is not short-circuited, the control circuit automatically sets the normal line current, e.g.

JlOmA via line L. If, on the other hand, the transmission contact b is closed, and thus the line L is short-circuited, this current flows as a holding current to the inverter circuit. Thus, when the current control occurs, the internal resistance of the control circuit would become, depending on the setting of the transmission contact b, switched between two values; when voltage adjustment occurs, the voltage would be switched back and forth between the two values.

Automatic line current setting can now be implemented as continuous current control. As such, it does meet the required conditions for power dissipation in the event of a short circuit, but it has at least the same power dissipation as with the previous connection technology. Besides, it is necessary to improve the transmission characteristics by locating control decelerations; this again requires an oi-shut-off current limitation during the deceleration time. The control circuit is shown in principle in Fig. 3. The direct current source UB conducts current through an internal resistor Ri, which is a resistor depending on the measured value of the current, through an ammeter AM and a load resistor Rb, which represents the subscriber loop. In parallel with the load resistor Rb is a transmission contact b.

The line current layout can also be implemented as a keyed current control. Its transmission characteristics correspond to continuous current control. The advantage is the possibility to reduce the power loss also in use, the disadvantage is the higher cost for the keying connection and the necessary equalization of the output current. A schematic diagram of the keyed control is shown in Fig. 5. The measuring device M measures and controls the current flow, depending on the deviation of the optimum value and the actual value from the keying ratio of the key contact k. Capacitor C acts as an output current equalizer.

Finally, the line current setting can also be implemented with voltage control. In this case, only as much voltage is supplied to the connecting line in each case as is necessary for the respective terminal and the resistor of the terminal to obtain the desired current. The actual voltage control - like the current control - can be continuous (Figure 4) or keyed (Figure 5). Its properties in terms of power dissipation and cost are similar to those of current control. Its transfer characteristics depend on the adjustment speed. In the current setting, the voltage control must ensure that at short wire lengths, the inductive consumer - such as a telegraph receiver magnet - does not become too attenuated, resulting in unacceptable distortions, i.e. too large a reduction in the reception area. For this reason, the internal resistance of the transmission circuit must have a specified minimum value (time constant for L / R current rise). If the internal resistance is not sufficient for current losses when the current drops with an oi-lock key, and in older telegraphers (high inductance L with a receiving magnet) the so-called "mixed keying", which can be implemented with an additional connection on the control panel side. This addition is connected between the connecting line and the converter connection to the telegraph conductor b1 and verifies the current flow through the connecting line in the write mode when the transmission contact b is in the disconnect position. If contact b is in the signal position, i.e. if the wire is short-circuited, the additional capacitance indicates the current path for the discharge of the wire capacitance. In addition to this, a capacitor is connected to the telegraph line b1, through which an additional current flows, which is generated from the energy released when the receiving magnet is cut off. This capacitor will be charged in a very short time. The back voltage thus formed, which is in series with the other auxiliary voltage, allows the auxiliary current to pass through the zero value early. The current drop thus becomes steep. Such an additional circuit, which combines the advantages of a disconnect and a short-circuit key, is described in German application P 2 138 576.2.

Voltage regulation can now take place quickly compared to the baud rate. In this case, the line current is measured at all times and with this measured value the voltage is adjusted so that the desired current flows. When the very high resistance of the subscriber (remote switching device) is switched off or switched on, the voltage rises to the maximum value required by the system, i.e. to the value which was also the transmission voltage in the prior art (e.g. 120V). The fully accepted wire length then gives the same transmission conditions as in the prior art. However, shorter wire lengths provide an improvement because the omission of the supplemental resistance of the wire allows the wire to charge faster.

9 60330

In another embodiment, the voltage regulation is slow relative to the baud rate. The line current is measured stepwise in the oscillating state; according to this, the transmission voltage is set fixed, i.e. the transmission voltage also retains its value during power-up when electrified. Only in the event of a prolonged power failure - eg when disconnecting - will the voltage rise to its systemic maximum value. Likewise, when the connection is built, it is first set to the nominal value with a deceleration; however, this deceleration does not have to be the same as in disconnection, but can be considered much shorter. In this structural example, the data transmission characteristics do not have to depend on the deceleration times of the control circuit. Also, the time constants of the filter circuits, which are, for example, necessary in keyed control, have no significance.

Another possibility for automatic line current setting is presented in German application publication 2 035 379 »in which a manually adjustable line replenishment resistor is replaced by an electronic circuit which sets the“ resistance ”to a value necessary for a given current. Such a control circuit is shown, for example, in Figure 7 (ELE). The connection works like a strongly time-delayed current control.

According to the invention, an unearthed DC power connection is used. If the voltage is fixed, as in current control, the maximum voltage according to the system is generated individually by the mains unit or converter per subscriber circuit, in which case the mains unit itself, i.e. the converter, can be arranged together for several subscriber fields. If the voltage is regulated, it is appropriate to concentrate the line current in the subscriber circuitry (e.g., in a hub drive) to generate line current in sleep mode, to reserve an additional voltage source that is common to all subscribers and does not need to be ungrounded.

In the embodiment according to Fig. 2, the unearthed power supply SV is provided with a keyed voltage control. A measured value sensor S is connected between the power supply SV and the inverter connection US for measuring the line current. The control panel-side auxiliary circuit TZ for implementing the "mixed keying" is connected between the electronic contacts bkl and bk2.

Another embodiment of the invention is shown in Fig. 6. In this connection, the ground symmetry and thus also the observance of the interference voltage requirements is verified by matching the unearthed DC power supplies and by galvanic isolation of the signal circuits. Galvanic separation is achieved by using photoelectric switching elements OKI, 0K2. The separate current supplies are supplied for several subscribers from a common AC power supply and consist of transformers Tr with rectifiers G12, G13 and filter capacitors C6, C7 (Fig. 7). In this case, in order to meet the interference voltage requirements, it is only necessary to smooth the pulse edges. The protective connections SS prevent the formation of too high contact voltages between conductors ai and bl and ground. As in known converter circuits, a holding resistor RH is installed. The transmission contact b is an electronic changeover contact formed of transistors T8, T9. If the transmission data SD has a value of "zero", transistor T8 is closed and transistor T9 is conductive. If, instead, the transmission data has a value of "one", transistor T8 is conductive and transistor T9 is closed. Connections A and B act as adaptations to the relay device.

Figure 7 shows a complete ungrounded converter circuit. As already mentioned (German application 1 911 252), the circuit includes a keying circuit AS of the RC keying circuit to which a trigger circuit is connected, in order to avoid subscriber-specific distortion compensation. Resistor R22 and capacitor C3 form a keying RC element. Through the pre-resistor R23, the complement-Schmidt trigger is controlled by transistors T11 and T12, which directly control the photoelectric switching element 0K2. The advantage of such a trigger connection is a very low power requirement in case the reception data ED has a value of "zero". The trigger thresholds are determined by the voltage divider R29j R24, R25 · The resistor R25 is for one-time equalization to adjust the minimum distortion in the structural group test on the test field. The emitter current of the photoelectric switching element 0K2 controls the output switch formed by the transistors T3 and T4 through the transistor T2. The connection A, which consists mainly of transistors T2, T3 and T4, forms an adaptation for the converter connection to the transmission location in the receiving direction. The corresponding arrangement in the transmission direction is formed by the circuit B containing the transistor T1. The transistor T1 acts as an input switch. Its collector circuit has a diode of the switching element OKI, the phototransistor of which controls the keying transistor T9 via the Darlington stage T10. Both transistors T8 and T9 form a transmission contact b. If the transistor T9 is blocked and the contact ui is closed, the transistor T8 becomes conductive through its base resistor R18. If transistor T9 is conductive, line current passes through diode D5 and then blocks transistor T8. The resistor R18 also has the function of a holding resistor RH.

11 60330

Electronic equalization is implemented by means of a capacitor CH and a resistor R32. These building elements, together with the key transistor T9, form a Miller integrator, which guarantees a slow, almost linear switching shape of the output signal. Resistor R5L works to eliminate oscillation tendencies. With an electrification rate of 50 Bd, this simple solution is sufficient. At a speed of 100 Bd, it is appropriate to use an active filter to generate a pulse.

The connection of the electronic line replenishment works like a strongly time-delayed current control. It is identical to the coupling disclosed in German application 2,035,379. The electronic wiring harness ELE is installed by means of a diode bridge Gil in the electrification conductor bl.

The function of the protective circuit SS is to prevent excessive contact voltages between the conductors ai or bl and the ground, which could arise from the earth leakage of unearthed discrete circuits. This is guaranteed by two central external voltage sources or a transistor connection with a zener diode nature and a bridge G1. At the same time, this connection, in cooperation with the structural elements R3, R35 and C5, protects against external, foreign voltages. Capacitor C5 also functions to increase the symmetry of the line terminal and to round off the transmission signals, which facilitates the fulfillment of interference voltage requirements.

The terminal change of the changeover contacts uT and u2 is derived from the transmission criteria. These criteria need to be monitored centrally from the point of sale. The relay can connect the polarity relay U via the control cable (polarity data UD).

For lightning protection, two protective conductors are reserved for conductors ai and bl against earth.

Claims (10)

1. Switching device for connecting telegraph subscribers to alternating current transmission devices and switching systems via wires of various kinds and length by means of direct current wiring, wherein the line current 1 is the wiring loop for each subscriber, adjustable to the prescribed value and the connection line is galvanically separated from the transmitting means, characterized in that for each connection line (L) an earth-free power source (SV) is provided and that in each subscriber connection in a telegraphing line (b1); an electronic device (EA) has been provided for flattening the flanks of the keyed DC power transmitted via the wires to the subscribers. 2. Device according to claim 1, characterized in that when the voltage is controlled, the pH station side is provided with an additional coupling (TZ) for carrying out the so-called. mixed key. Device according to Claim 1 or 2, characterized in that a protective coupling (SS) is arranged between the telegraphing trees (ai, b1), which prevents the occurrence of an unauthorized contact voltage to ground. Device according to any of claims 1-3, characterized in that the electronic flake coupling (EA) is designed as an emitter follower, the base of which is connected to at least one RC circuit. Device according to any of claims 1-3, characterized in that the electronic flake coupling (EA) is designed as a Miller integrator (T9, CM R32). Device according to any one of claims 1-3, characterized in that the electronic flake coupling (EA) is designed as an active low pass filter.