DE1073073B - Circuit arrangement for remote control systems for the transmission of grain mandos with a control station and several receiving stations - Google Patents

Description

GERMAN

The invention relates to a circuit arrangement for telecontrol systems in which the control of individual Stations is done by transmitting pulse trains. In a known remote control system from an overland plant, the plant to be remotely controlled is selected with the dial and through this first pulse train released by the remote control receiver of the desired substation while in the remaining works the recipients remain blocked. Dialed by a second with the dial A certain switching command is marked with a number. Another series of impulses is transmitted, which acts in the substation on 'the relevant' command relay. A guarantee of the selection a certain receiving point and a guarantee of the command transmission is with this arrangement but not achieved.

In the case of other known systems, security is provided according to the complementary procedure. Included a series of pulses is transmitted from the control station to a station in preparation for a command. From this station a series of impulses is sent back to the control station, whereby the execution of the Commands are only issued when the sum of the two pulse series results in a certain constant number of pulses added. The use of pulse transmitters in every station requires a lot of effort on the one hand on switching means, on the other hand, if the impulses sent for command preparation get mutilated to the station, these impulses make a wrong command preparation. If now the pulses sent back by the station are also subject to distortion, so that they are in the control station lead to the correct addition of the constant sum, an incorrect command is triggered.

It is also known that the selection and the issuing of commands for the purpose of securing by transmitting a to carry out a double pulse series, the two pulse numbers of which add up to a constant sum. Both series of impulses are received by two correspondingly switched selectors, their immediate Working together closes a circuit that initiates the necessary switching operations. If several commands are to be controlled in several stations connected via a connection line a selection of the stations and within each station a selection must be made of the corresponding command. With each selection must be the assurance guaranteed ". In the known systems, this requirement requires a lot of voters and other switching means.

_ In another known system, a single Transmit impulse series, which both the circuit arrangement for telecontrol systems for the transmission of commands

with a control point and several receiving points

Applicant:

Standard electrical system Lorenz

Stock corporation,

Stuttgart-Zuffenhausen,

Hellmuth-Hirth-Str. 42

Dipl.-Ing. Helmuth Stobbe, Ludwigsburg,

and Herbert Heitrnann, Stuttgart-Zuffenhausen,

have been named as inventors

the desired station as well as the relevant command. This series of impulses will be above all Stations sent out common connection channel. The desired station is switched on and the All other stations are blocked. With this system, the at the individual stations existing voters have as many outputs as the total number of switching commands in the entire remote control system should be transferred. Only those voter exits are in each of the individual stations that are assigned to the individual switching commands for the relevant station. The rest Voter exits remain unused.

If, for example, in a remote control system with a control center and three substations, 10-part If a selector is used, it is practically only possible to issue three switching commands to two substations and to transmit four switching commands to the third substation. At substation 1 are then only the selector outputs 1 to 3 connected while In station 2 only the voter outputs 4 to 6 and in station 3 the voter outputs 7 to 10 that can be exploited. Is there a larger number of substations and should transmit more switching commands to the individual stations then this known arrangement requires a very large amount of switching means.

909 709β62

The impulse transmission is secured by that a constant number of pulses are sent and received. For this purpose, the Two corresponding voters are provided for each station. This way of ensuring the impulse transmissions The above-mentioned number of voters doubles again.

The invention shows an arrangement which reduces this high expenditure, without the safeguarding the selection process and the command. You achieve this by the fact that the the control station in the form of two consecutive partial series of pulses with one for all commands commands issued with the same total number of pulses at the same time in all receiving points be recorded, but that by the combination of the first two, for the selection of the receiving point serving partial pulse series only in this Combination corresponding receiving point switching means come into effect, which are used in this receiving point to receive the pulse series Return facilities to their original position and prepare the receiving center so that upon delivery of the two following, a certain switching process characterizing partial pulse series with turn the same total number of pulses via the same pulse pick-up devices, the desired switching process is carried out. Due to the signal transmission in two stages, the disadvantages of the known Arrangement avoided. The invention has particular features over the above-mentioned known arrangements the advantage that, despite the guarantee, the electoral effort is significantly lower, since after admission of the first two partial pulse series, the voters are returned to their starting position and ready for recording further impulse series, which are used to issue commands, are available. So it is z. B. possible To reach ten substations via 10-part voters and ten different switching processes there initiate.

Counting magnets are used as switching means, which record the pulse series an electromagnet with one pull-in and one drop-off winding and several juxtaposed There are partial anchors that are connected in sequence and the spring sets assigned to them actuate. After recording the first two series of pulses, these counting magnets identify one specific station in that only the test switch can respond via its set contacts, which is defined by the contact setting "of the counting magnet. The test switching means switch according to their If the counting magnets respond to the two subsequent pulse series in their zero position back and energize another switching means, which only in the so marked station that the command containing pulse series can come into effect. According to a further embodiment of the invention when the command is executed in a station, switching means come into effect, which the Initiate notification of such a change in status to the control station. This identification becomes the control point in the form of a continuous tone for wireless transmission or in the form of a permanent earth for transmission accomplished via connecting lines. The result that comes into effect in the control unit Switching means initiate a check of the switching states of all stations or only in the station that was previously was selected. It depends on whether the switching states are checked in all or only in one station from whether certain switching means, z. B. a button, were turned on or not. According to a further embodiment of the invention take with delivery of a Switching order when the button is pressed switching means one of the two, which makes the selection of a station Pulse series and prepare a circuit for further switching means, which of the selected Are assigned to the station. This prepared circuit comes through after the command has ended the application of the permanent earth to the effect, whereby switching means are switched on, which the test of the Initiate switching states of the previously selected station. These switching states are checked in such a way that the station is automatically selected again and switching means in this station the Scan positions individually, with further switching means the individual switching states in the form of The identifier is transferred to the control station and evaluated there for support indicators. According to Another embodiment of the invention is when a switching command is issued when the button is not pressed Execution of the command stimulates the control station to check all positions of all stations.

Further useful details of the embodiment of the invention are that shown in FIGS Referring to embodiment, which will now be described in more detail.

Fig. 1 shows the principle of the pulse remote control as a block diagram;

Fig. 2 shows the circuit arrangement of the control station;

Fig. 3 shows the circuit arrangement of the stations. Let it now be with reference to Fig. 1, the principle of Impulse remote control explained.

The necessary commands are sent from the control station in the form of pulses with the help of the JS pulse transmitter. A distinction is made between the following pulse series:

Command impulses K ₁

Error registration pulses F,
General interrogation pulse G.

The stations acknowledge this series of impulses with the help of the DE continuous tone receiver, which receives the following continuous tone:

Continuous acknowledgment tone Q,
Fault registration continuous tone F,
Continuous general interrogation tone G.

Correspondingly, stations 1, 2, etc. contain the continuous tone transmitters DS required for emitting the continuous tones and the pulse receivers IE for receiving the pulses sent out by the control station. All the stations can be parallel or in series. The following transmission paths can be used as a connecting line between the control unit (control center) and the stations:

1. Direct cables or overhead lines,

2. telephony lines affected by high voltage,

3. four-wire carrier frequency channel,

4. Four-wire radio channel.

When using transmission paths according to numbers 3 and 4, those indicated in FIG. 1 are indicated Pulse transmitter and receiver required.

Each command consists of two series of impulses. A station is selected with the first series of impulses, while a command is executed or prepared in this station with the second series of pulses

ι υ / 3 υ / ό

5 6

will. Each of these series of impulses consists of two energized by pressing the command key K 1

successive partial pulse series was a total of eleven, so that ten pulses in the third pulse series

Pulses so that z. B. the stations as follows and emitted a pulse on the fourth pulse series

be selected: will. During the test after the fourth series of pulses

Station 1 10 + 1 pulses P ^{5 s report on}

Station 2 9 + 2 pulses +, μ 111, «21, PA (I), atV, eil, sm (on position

Station 3 8+ 3 impulses 1), P, -

Station 4 7 + 4 pulses _n , ^,., -,., - ^, · _π ., - ^, - ^

Station 5 ^au 6 + 5 pulses? F the relay, the relay P PA of through contact

Station 6 5 + 6 impulses ^Io £? ^TI the_ relays GI ₁ AN, EI ₁ AC are de-energized.

Station 7 4 + 7 pulses ⁰ ^ command has been issued.

Station 8 3 + 8 impulses should now generate the

Station 9 '"2 + 9 impulses commands triggered processes on the basis of

Station 10 '.'. '.'. '.'. '.'. '.'. '.'. '.'. '. 1 + 10 pulses Fig. 3 will be explained

15 The pulse series sent by the tax office

Only when these two partial pulse series eleven are picked up by relay A in the stations.

Supplementing impulses will be a station for recording men. With the first pulse of the first series of pulses

The following, also made up of two partial pulse series, becomes the drop-out delayed relay V via contact a II

existing impulse series prepared, while all excited, which holds itself over the impulse series. Above

other stations for the inclusion of commands 20 + al Will viii SMl

be blocked. The command itself is like '' '' '

mentioned, from a two-digit series of pulses, which is controlled by the counting magnet SMl. After the first is just as composed as the series of pulses for the one-time drop in relay A , the stations are selected via the contacts. al, ν IV the relay C switched on, which is just-Further details should now be with reference to Fig. 2 25 if the pulse series holds. At the end of the first and 3 are described in more detail. Partial pulse series drops relay V and then relay C

away. During the time that relay V has dropped out, relay C

1. Transfer ^is a ^{command, but still} excited> is

Should z. B. Transfer a command to station 1 30 >>>>>

are, the relay Vl are energized and over in the control station (Fig. 2)

Keys Gl and Kl pressed. Via the key Gl + pi vll Vl -

the relays G1 and ON and the key Kl ' ^V ''

the relays El and AC energized. Maintained via the contacts anl. Contact wants prepares the counting magnet

and ad the relay interrupter X ₃ Y is activated 35 SM 2 for receiving the second partial pulse series.

permit. With contact xl the pulses become the The second partial pulse series is thus transferred to the counter

Transfer stations. Contact .tTV switches the counting magnet SM2 . The attitude of both

magnets SM continue in pulses. If the counting magnet reaches SMl and SM 2 , the indicated

magnet SM the routed step 10, it speaks about the selected station, since the test relay P is only connected to this

+, ^ II, "2ILg-lX, .m (at position 10), P, - ⁴ ° position alone above

, ",. "", _Ύ,. ,, ",. +, rV, sml (on position 10), sm2 (on position

the relay P on. Contact p I interrupts the relay- j _u ^ _v jjj- ρß \ _

breaker X ₁ Y. Contact pill switches the relay ^h ' ^K ''

PH and contact p II the discarding development of the counting can come into effect.

magnet 5 "M (II), so that it is in its normal 45 For station 2, for example, which is switched back by the digits 9 + 2, whereby the current is controlled, is via a contact of the relay R circuit is interrupted again for the relay P. After direct earth only on the line that passes through the con-drop of the relay P, but when the relay PH _{1 is} still energized, clocks sm 1 (9) and im 2 (2) to the test relay P is going through station 2, so in this way a safe one

_i_ i-wT αζ, τττ tto "iv j," tt ixrs 5 ° selection of the individual stations is given.

+, p Vl, ph, Li.!, U2, ul V, * oll, Wi, - ,,., _T _, __ ... -n? · Η ' 1 ii j.

^rrr With contact pH the relay R is switched on,

Relay U 2 energized and via its own contact that after the test relay P has dropped via its

m2IV held. After the relay Pi has dropped? will keep your own contact rl. Contact pV closes one

Relay breaker Z, Y started again. According to the circuit for the reset windings of the counting

Sending a pulse speaks about 55 magnets SMl (IT) and SM 2 (II), which as a result

+, Ulli, u2II, glI, sm (to position 1), P ₁ - return to their zero position _<

The two following partial pulse series that make one

Relay P on again. The further transmission of the specific command in the selected station

Impulse is suppressed and the counting magnet SM ₁ correspond to relay A in the same way

as already described, postponed. Recorded over 60. The setting of the counting magnets SM1

+, pIV, phU, Ul ₁ «2ΙΠ, pall, Wi ₁ - £ ^{nd SM2 εΓίο1} ^ ⁱⁿ the manner already described.

It was assumed that the third and fourth luminous

the relay Ul is energized and its own pulse series of ten pulses or one pulse

Contacts ul IV and u Uli kept. Persist with contact. Accordingly, the contacts sm 1 (10)

ulV the holding circuit for the relay U2 65 and sm2 (i) is switched on, so that over

interrupted. The relay interrupter X ₁ Y is switched to _{+> rm ciy sm2 (on} position 1), sml (on

Relay PH relay started again. The third position 10 ") rV Gl-

and fourth pulse series are in the same way as ^ö ''

already described, sent, only the relay P checks after the release of the relay C relay G1 is energized, itself

in this case via contacts of relay EI ₁ which holds 70 with its winding III via contact g 1 II and

1 Ό / Ö Ό / ö

initiates or directly executes a switching command with its contact gll. At the same time is over

-τ-, J-III, cIV, viii, P (I), relay P energized so that about

+, rl, WlIII, pill, R (II), -

the winding (II) of relay R is counter-excited and relay R drops out. In the present example, the relay Gl switches on a relay Kl with its contact gll, which triggers any process and with its contact kl switches on a relay Fl which, as will be explained later, is used to display the switching state.

2. Acknowledgment of the executed command

The switched on relay F 1 initiates the feedback to the control station. Above

+, wll, / 11, / ill, T ₁ -

relay T is energized. Contact il is used to connect permanent earth to the connection line. If the commands are transmitted via a radio channel or carrier frequency channel, the relay T initiates the transmission of a continuous tone to the control station in a manner not shown. By applying the permanent earth to the connection line, the relay C in the control station (Fig. 2) is switched on. The relays U 2 and AT are excited via its contact cXl and held via contact oiVI. If the ET key was pressed when the command was given in the control station, the counting magnet had AMA. After the relay U 2 has responded, the second partial pulse series, in the example under consideration, a pulse, is recorded and station 1 is thus identified. In this case, the individual command positions are only queried in the previously controlled station. When the relay AT responds , the circuit of the relay W is interrupted and over

+, aiii, w II, line Ll

A longer impulse is given to the stations via the release time of the relay W. After the relay W drops , over

+, phl, pl, yl, wl, X ₁ -

the relay breaker X ₁ Y is left on , whereby pulses are transmitted to the remote-controlled stations. With the emission of the pulses: as already described, the counting magnet SM is controlled via contact χ Vl. In addition, since relay AT is energized, over

+, atlll, xlll, ull, AM2, -

the counting magnet AM 2 is also set. This counting magnet identifies the support indicators corresponding to the selected station 1, on which the switching states are displayed when the individual command points are checked. Above

+, oiVII, om.4 (l), ami (O), Gl ₁ AN (T), pall, Wi ₁ - ■

Relay Gl had responded, so that after a pulse has been sent, which activates the counting magnet .9M its contact sm (1), the following circuit is closed:

+, will, «211, gll, StHr (I), P, -.

Relay P is energized. Contact p I switches off relay interrupter X, Y. ■.

In the station (Fig. 3) relay A receives the long pulse given over the line Ll. Contact all opens the circuit for the relay W for a long time, so that it drops out. After relay A drops out, relay C is energized and the pulses sent by the control station, in the example under consideration, a pulse, are triggered

+, oil, will, cIII, KM ₁ - ίο picked up by the counting magnet KM . Above
+, rIV, km (I) ₅ J-VI, w VI, P (I), -

the test relay P is energized. Contact pll energizes relay R, and contact plV opens the circuit for relay T ₁ which drops out. Contact pV switches on the reset winding of the counting magnet KM (II), so that the counting magnet KM is switched back to its zero position.

In the control station (Fig. 2), when the relay P with contact / »II responded, the counting magnet SM (II) was switched back to its zero position and the circuit for the relay P was thus interrupted. Contact pill interrupts the circuit for relay PH. The relay [71 is excited over the fall time of this relay PH and held by its own contacts u ITII and u HV. Contact «II switches the circuit from the counting magnet AM2 to the counting magnet AM 3 , so that the pulses emitted by the relay interrupter X ₁ Y , which is switched on again when the relays P and PH drop out, are picked up by the counting magnet AM 3 via contact xlll. The Zählmagnet AM3 switches over its contacts sequentially either the relay Al ^ to 410, or the relay Bl to # 10 so · that the support Indicator a particular station indicated by the Zählmagneten AT 2 can be adjusted. The setting of this support flag indicator in response to energization of the relay Al to AlO and Bl to 510 is controlled from the station by the finding of the change of state of the command execution indicating switching means Fl to FlO (Fig. 3).

As already mentioned, after a certain station has been set, individual interrogation pulses are transmitted from the control station to this station. The KM counting magnet is incremented one after the other. After receiving the first impulse, the contact km (1) is actuated, so that the following circuit is closed:

+, rVI, km (l), J-IV, / HI, Hl ₁ P (II), -.

Relay P responds and with its contact plV opens the circuit for relay T _1, which is switched off. Contact ti interrupts the circuit for the relay C in the control station (Fig. 2), so that there over

+, aw3 (l), Cl ₁ ^ l ₅ -

Relay Al is actuated and one winding of the support indicator is switched on over oll and on 2 (1) and the support indicator thus indicates the change in status in station 1. After the second interrogation pulse, the counting magnet AM 3 has actuated its contact oot3 (2) in the control station (Fig. 2) and the counting magnet KM has actuated its contact km (2) in station 1 (Fig. 3). The relay F.2 indicating command 2 is not actuated. This means that when checking in station 1 via contact km (2), the test relay P cannot be energized, since the / 1 II contact, not shown, is not switched.

Thus, relay T is excited via contact plV and therefore

1 U /

accordingly energized via contact il relay C in the control station, so that over

+, ßw3 (2), cIl, B2, -

the relay B , not shown, is energized and thus the associated support indicator for displaying a certain state is switched on via a contact of the relay B 2 , ie in this case it does not indicate a change in state. Depending on whether the relay T in station 1 is switched off via relay P or not, one or the other winding of the corresponding support indicator is switched on or not in the control station for each individual command via relay C. After checking the last command position, ie after the tenth pulse, over

+, MlIT, w2L atV, L ₁ atTV, sm (10), P ₁ -

the relays P and L energized. The relay interrupter is switched off with contact pi , and the counting magnets AM 2 and AM 3 are reset with contact / I ao , and relay PA (III) is switched on with contact / IV , whose contact pall triggers the trip.

If the ET button on the control unit was not pressed when the command described above was sent and the AM 4 counting magnet was not set, then all stations are checked for their switching status after the command has been executed. After returning the continuous tone or when using lines after applying the earth via contact 11 in any station in which a change of state has been carried out, relay C is energized in the control station.

Contact cXI closes a circuit for relays U 2 and AT ₁ which are held by contact at VI. Above

+, oiVII, ow4 (0), awl (0), Gl ₁ AN (I), pail, Wi, -

the relays G I ₁ AN are energized. As already described, station 1 is now controlled and the command positions are queried there. After querying all positions in this station, the last contact of the counting magnet SM relay L is energized in the circuit already described. Contact / II closes a circuit for the counting magnet AM I _1, whereby the contact at 1 (1) closes and relay G 2 is switched on. This initiates the control and query in station 2. After completing this query, the same process takes place for stations 3 to 10. When querying the last command positions in the last station 10, the relay L responds again and switches the counting magnet AMl one step further with its contact / II, ie the last contact on 1 (10) is activated. This contact ow 1 (10) energizes the relay PA (II), whereby the tripping takes place.

3. Display of changes that were not made from the control _panel

If a change occurred in any station, so that the variation indicative Fl relay is switched on until PlO. Relay T is energized and earth is given to the line Ll to the control station. Relay C responds and switches on relays AT and U 2 . As already described, the command positions are queried in all stations and any changes are displayed on the indicator panel.

4. General inquiry

The already described check of all command positions can also be initiated in the control station by pressing the general query key AT. The processes are the same as already described.

Claims (20)

Patent claims: 1. Circuit arrangement for telecontrol systems for the transmission of commands, with a Control station and multiple receiving stations using pulse trains to select the Receiving points and for the transmission of commands, characterized in that the Control point (Fig. 2) in the form of two consecutive Partial pulse series with a total number of pulses that are the same for all commands .Commands are recorded simultaneously in all receiving points (Fig. 3), but that through the combination of the first two partial pulse series serving to select the receiving point only in the receiving point corresponding to this combination switching means come into effect, which in this receiving point the return the devices serving to receive the pulse series to their starting position and prepare the receiving office in such a way that when the following two are submitted, a specific Switching process (command) characterizing partial pulse series with again the same total number of pulses The desired switching process is carried out using the same pulse pick-up devices will. 2. Circuit arrangement according to claim 1, characterized in that as switching means for Recording of the pulse series for the control, acknowledgment and execution · Counting magnet used are each made of an electromagnet with a pull-in and release winding and off consist of several anchors arranged next to each other, which are connected in sequence and actuate the spring sets assigned to them. 3. Circuit arrangement according to claims 1 and 2, characterized in that after receiving the first two partial series of pulses, the counting magnets (SMl ₁ SM 2) identify a certain station in that via their set contacts (sm2 (1) ..., Sml ( 1) ...) only the test switch (P) of the station defined by the contact setting can address. 4. Circuit arrangement according to claims I to 3, characterized in that the test switching means when it responds, _{the counting magnet (SMl 1} SM 2) switches back to their zero position before receiving the two subsequent partial pulse rows and another switching means (R) brings into effect which only lets the pulse series containing the command come into effect in the marked station. 5. Circuit arrangement according to claims 1 to 4, characterized in that when executing a command or a change in the state in the station switching means (Fl to FlO) come into effect, which initiate the transmission of this change of state to the control station and cause a display there . 6., circuit arrangement according to claim 5, characterized in that the at a state 909 709/362 1 U / 3 change in the station to take effect switching means (Fl to FlO) switch on another switching means (T), which places permanent earth on the line leading to the control station (L 1). 7. Circuit arrangement according to claims 5 and 6, characterized in that by applying Permanent earth to a line switching means (C) of the control station a check of the switching states initiate in all stations or only in the previously selected station. 8. Circuit arrangement according to claims 1, 5 to 7, characterized in that the checking of the switching positions in one or in all stations depending on a switching measure (BT) is carried out before submitting a switching order. 9. Circuit arrangement according to claims 1 and 8, characterized in that when a switching command is issued in any station when the button (ET) is pressed, switching means (AM 4) record and store an ao of the two partial pulse series making the selection of a station and a circuit for Prepare switching means (Gl to GlO) which corresponds to the selected station. 10. Circuit arrangement according to claims 1 to 9, characterized in that this prepared circuit is closed by switching means (AT) which are switched on by applying the permanent earth via the switching means (C) which comes into effect. 11. Circuit arrangement according to claims 1 and 10, characterized in that this switching means (AT ) switches off a closed-circuit relay (W) in the control station (1 and 2) and transmits a long earth pulse to all stations over the fall time of this closed-circuit relay. 12. Circuit arrangement according to claims 10 and 11, characterized in that the long earth pulse causes the fall of the quiescent current relay (W) in all stations, whereby switching means (KM) for receiving the selection and query pulses are switched on preparatory. 13. Circuit arrangement according to claim 10, characterized in that after the preparatory circuit has been closed by switching means (AT) and the closed-circuit relay (W) drops in the control station, a relay interrupter (X, Y) is started and depending on the switched-on switching means (G 1 to G10) a certain series of impulses is sent to the stations. 14. Circuit arrangement according to claims 12 and 13, characterized in that switching means (KM) in the stations record this series of pulses, but only close a test circuit in the station corresponding to the series of pulses, and switch means (P, R) to identify this station . 15. Circuit arrangement according to claims 12 to 14, characterized in that after the identification of the station selected by a series of pulses, the switching means (KM) is switched back to its zero position and with renewed recording of individual, successive pulses on the command positions characterizing contacts (f 1 to / 10) checks every single switch position in the selected station. 16. Circuit arrangement according to claims 12 to 15, characterized in that when checking the switching position depending on the relays characterizing the switching positions (Pl to FlO) a switching means (P) comes into effect, which another switching means (T) to identify the Switching positions cause either earth to be connected to or disconnected from the connecting line. 17. Circuit arrangement according to claims 12 to 16, characterized in that via switching means (C) of the control station, the indicator transmitting the switching positions of the stations to switching means (Al, Bl ... AlO, BIO) acts in such a way that one of two individual windings Support indicator (SZl to SZ10) is switched on. 18. Circuit arrangement according to claims 1 to 17, characterized in that when a station is selected for testing the switching states, switching means (AM 2) of the control station provide the supporting indicators corresponding to this activated point and further switching means (AMS) of the individual switching positions corresponding to the windings of the switching means (A 1, Bl ... AlO, BIO) that switch on the supporting indicators, one after the other in synchronism with the switching means (KM) of the station. 19. Circuit arrangement according to claims 1 to 6, characterized in that when there is a change of state in any station, switching means (T) initiate a display in the control station, whereby all stations on their switching states be queried. 20. Circuit arrangement according to claim 19, characterized in that this general query can be initiated from the control station by pressing a button (AT). " Considered publications:
Austrian Patent No. 136 574;
German Patent No. 927 883;
BBC announcements, April 1953, pp. 112 to 123. 1 sheet of drawings © 909 709/362 1.60