DE1449047A1 - Self-monitoring device for warning systems - Google Patents

Description

PATENT LAWYERS DR. ING. KARL BOEHMERT DIPL-ING. ALBERT BOEHMERT ~

DIPL-ING. GÜNTHER EISENFUHR 1449047

28 BREMEN, FELDSTRASSE 24 FERNRUF (0421) 4917f

Dr. Expl.

ft »! nh. <fckentoi Hamburg 126083 Bank account ι Bremer Bank, Bremen, account 1449

THE MAEQUAEDT COEPOEÄTION

T 4-33 28 Bremen, ₁₀ . J _11n I 1964

THE MAEQUAEDT OOEPOEATION, Van ÜTuys, State of California (V.St.A.).

Self-guarding device for warning systems

The present invention relates to warning systems } as used at rail crossings to display warning signals of an approaching train will. The invention particularly relates to a time-dividing one Self-monitoring device for such systems, which the operation and performance of the entire system is periodically checked in order to To be able to quickly identify possible failures and to ensure perfect protection by the warning system to ensure.

009832/0076

It has already been proposed a warning system for rail crossings that a predetermined time before the train reaches the intersection, signals and / or barriers activated »This well-known system is a rail crossing warning system, in which the rail tracks with an alternating voltage signal of constant amperage be fed. The rails then act as a transmission line that is short-circuited by the train A detector attached to the rails is responsive to changes in the AC voltage signal, which result from the approach of a train, whereby the speed and position of the approaching train is continuously monitored »Regardless of the speed of the approaching train, the Warning system for rail crossings, when the train will be a given time away from the crossing, and then triggers the warning devices at the intersection You can choose between the approach of an incoming. Train and the activation of the warning signals any time interval can be selected. If the approaching train stops before it reaches the intersection, it interrupts the warning system sends out the warning signals and enables the crossing traffic to run away · If the Train moving towards the intersection again, actuates the

00 ^ 232/0076

Rail crossing warning system immediately the warning signals again In this way, for the crossing traffic, it does not matter whether there is a fast moving express train or a slowly moving freight train is approaching the rail crossing, there is a sufficiently long warning time

Although the warning system for rail crossings shown and explained in the above-described application represents a considerable step compared to the prior art, the device according to the present invention improves its effectiveness and the safety of the warning system for rail crossings is further increased by automatic self-monitoring for the correct functioning of the system is specified

The self-monitoring device according to the present invention simulates a train approaching at very high speed in periodically successive time segments. This simulated signal operates the entire crossing warning system and causes it to respond in a normal manner, the operation of the crossing signals and / or barriers being interrupted only during the self-monitoring cycle

009832/0076

Basically, it does not work satisfactorily, there is a standby system switched on. that actuates the intersection signals. Since the apparent speed of the simulated train is very high, the time to the predicted arrival time is very short. For this The reason is that required to test the system Tent relatively short, in a typical example on the order of a fraction a second. In a preferred embodiment of the invention, the self-monitoring cycle becomes automatic repeated every few seconds · This way, the performance of the system is in practical alien! "all continuously monitored.

The invention is described below on the basis of its application described for a warning system for a rail crossing. However, it should be emphasized that the

new and improved self-monitoring device according to of the invention also applies to other types of prediction devices or advance warning systems can be used, for example in automatic time-to-destination navigation computers and / or other arrival time forecast - devices and analog computing devices that contribute to the solution of equations of form

(1) f dl ·. + L- O

00983270076

(2) aT ² + 2VT - 2L - O

serve, with

T is the time required to move an object to arrive at a given point, "

L is the distance of the moving object from the given point,

V is the speed of the moving object towards the given point «-

a is the acceleration of the moving object to a given point. to »-

It is therefore an essential object of the present invention to provide a new and improved warning or prediction system indicate that has a greater reliability compared to the previously proposed systems.

Furthermore, with the invention a new and improved self-monitoring device, which is in these Use warning or goal prediction systems let “indicated will.

It is also an object of the invention to provide a warning

009832/0076

ΊΛ49047

system for a rail crossing to specify the one has better reliability.

The aim is to use a new and improved one Self-monitoring rig the reliability a warning system for rail crossings is enlarged

Finally, a new self-monitoring device is intended

can be specified for analog computing circuits in which the time scale during the test and test input signals compared to normal or real input signals for the Eeehenschaltungen significantly reduced thereby enabling multiple or repeated monitoring of the device without the standby the device, the normal input signals reduce considerably. ·

The general aim is to provide prediction or advance warning devices to improve"

Another general object of the invention is to provide a warning device for rail crossings, which are the night @ ile of the previous devices and overcomes procedures for the same purpose »

H49047

The new eyes see new features of the invention detailed in the attached claims. The present invention can, however, in its structure and in its mode of operation together with other objects and advantageous features best with reference to the following description in conjunction to understand with the accompanying drawings «In the drawings, like reference numerals are used for each other appropriate parts provided.

In the drawings is:

Figure 1 is a simplified block diagram of a Warning system for rail crossings to which the present invention is applied can be;

Figure 2 is a graph showing the total time on the rail versus the distance shows representing tension on a slow train}

Fig. 3 is a graph showing the

Total time on the rail versus the voltage representing the distance for shows an express train;

Fig. M - an exploded block diagram

of an advance warning system for rail crossings with the self-monitoring device according to the invention;

Fig. 5 is a block diagram of another embodiment the invention;

Fig. 6 is a block diagram of another embodiment the invention;

7 shows a circuit diagram for explaining the invention;

009832/0076

U 490-47

Fig. 8 is a graphical representation of the used Waveform showing the modulation of the simulated input signal and facilitates the explanation of the invention.

1 of the drawings is a simplified block diagram of a warning or prediction system for rail crossings See to which the present invention can be applied · As the warning system for the rail crossing itself does not form part of the present invention, of course only as many details are explained and information about the mode of operation is given, how to fully understand the here described Invention seems necessary.

The warning or prediction circuit includes an oscillator 1, the output of which goes to rails 2 and 3 is conducted via a rail power amplifier 4 The power amplification circuit contains a constant current generator, the one alternating voltage output with essentially constant current to the rail track feeds. In a typical embodiment, the AC voltage supply signal beeltzt a frequency between 86 and 645 Hz and a current of 200 mA. The system sends and receives at the same point and used the rail rank as impedance · the connection point · are

BATH

009832/0076

1U9047

marked with P and P ¹ "· The receiver measures the voltage produced by the constant current generator (oscillator 1 and amplifier 4) on the rail track. When the rails are free, an alternating current bridging resistor 5 forms at a distance 3 ^ ₂ - between P and P ¹ the rails 2 and 3 have a low impedance on the rail track, which corresponds to a train standing in a maximum distance. The recorded signal is filtered by the band filter 6 in order to switch off bulk and extraneous signals. and reactive voltage components together. Only the reactive voltage component - is measured »This prevents errors that can be attributed to the high rail connection resistance« The reactive voltage or phase component is converted using an AC / DC voltage converter / · This voltage (Ejj) is a DC voltage that corresponds to the reactive voltage component of the AC voltage received at points P and P ¹ praises. The direct voltage is then differentiated by the differentiator 8, whereby a voltage proportional to the train speed (E ^) is obtained.The train speed voltage (E ^) is then multiplied by the warning time T and added in the summing amplifier 9 to the distance voltage (E ₁₁ ). The diatane voltage (E ₃₅ ) is taken directly from the alternating voltage /

/ into a DC voltage E

000932/0071

U49047

-ίο - ■■ ·,

Direct voltage converter 7 passed to the summing amplifier 9. If TE is equal to or greater than _D E _D, then the relay driving circuit 11 is energized, which in turn sets the signals or barriers at the junction in operation.

If there is no train on the line, the maximum and constant signal is obtained; therefore E ₀ -O and there is no warning. If the train passes the points

When PP ¹ approaches the route, E _D decreases while • ■ · ■■

Ep on one given by the train speed Value grows.

The two conditions mentioned above are shown graphically in FIGS. In lig. 2, the DC voltage EJ ₃ , which corresponds to the distance of the train from the points PP ·, is plotted as the ordinate. The total time that the train shorts the transmission line (the track) is plotted on the abscissa. If the train is far from the intersection, the distance or distance voltage is Έ-. the maximum value drawn in at 12 · As soon as the train runs over the bridging resistance on the track, the distance voltage begins to decrease ο The point at which this happens is in the graphic

009832/0076

1U9047

- li -

Representation denoted by 13 · The differentiated distance _{voltage (E D} ) multiplied by the fixed warning time (T) is shown at 14 and corresponds to TEp. If this value corresponds to the distance voltage (E ^), as shown at 15, the warning signals are activated at the intersection. This provides a fixed warning time! T.

As can be seen in Fig. 3, a faster train delivers a larger relative speed signal 16 '. Therefore point 17 appears at Ej *' TEj ₅ earlier than the corresponding point 15 in Fig. 2, while the warning time T remains the same.

As the train ^{approaches the points PP 1} on the track at which the constant supply voltage is applied, the impedance of the track decreases continuously from these points in the direction of the train. This follows from the fact that the train unites the track Short-circuit forms, which moves towards points PP ¹ · The moving short-circuit changes as long as the train ^{approaches points PP 1} , the resistance of the circuit constantly · By measuring the voltage applied to the track, an indication of the distance is displayed of the train from the points at which

009832/0078

the voltage is applied. The change in the voltage phase as a function of time provides an Geschwindigkeiteinformation, and the second derivatives of the voltage information provide information about the acceleration of the train is · In Fig. 4 is a block diagram of a practical Vorwarnsystemes shown «3- ⁿ the Selbstüberwachungevorrichtung according to the invention is built in. Since all of the units represented by a block in FIG. 4 correspond to the numerous forms of apparatus for similar functions which are well known to those skilled in the art, no further circuit details are given here.

The one from the two rails 17 and 18 and the load resistance existing rail track can be viewed as a transmission line. He is given in a Distance from the feed point (P-PV) from a narrow-band bridging resistor 19 for AC voltage shorted. As already mentioned, the Distance at which the bridging, contrary to 19 arranged from the rail crossing let, ale "Ir ΜΑΣ * denotes, and it depends on the maximum speed of the train and the desired warning time at the intersection » The total impedance on rails 17 and 18 includes'

009832/007

Resistances and inductive components. The ratio between the total impedance and the active resistance components "determines the phase angle, and for a typical rail transmission line this angle is around 70 °. If the system responds to phase changes, it can be made immune to changes in the active resistance components, which in practice are due to environmental influences The AC supply signal is taken from the oscillator, the output of which is connected to a phase shifting network 22 is when a pure active resistance load is used instead of the rail line ^{impedance at the points PP 1.} The output from the network 22 is via the modulator 25, the mode of operation of which is described below in connection with the operation eb of the self-monitoring device is described »routed to the power amplifier 24.

Ün fiterstand 26 connects one side of the performance vtrstitkera 24 at point P * with a rail (for example of the rail 18) * The other side of the line

009832/0078

1449 Wl

The power amplifier 24- forms a constant current generator together with the resistor 26. The output of the constant current device is used to generate a voltage which is proportional to the distance of the train from the points PP ' * As the train approaches the crossing, the impedance of the track in the direction of the train is continuously decreased. Since the current is kept constant, the voltage increases. By measuring the changing voltage on the track, an indication is made about the distance of the train from the points PP '. The ₌ change of this tension with time provides information about the speed and the second

Deriving this voltage provides information about the acceleration of the train »

The narrow DurchlaJBband of the bandpass filter 27 is located around the oscillator frequency around, and this filter is through the attenuator 28 with the same points of the ^{ffi #} - verbün ■ rail track as the Könstantstrpmgeneratör - ^^ the "The received signal is by the movement of ^{the;. T} train 29 modulated in the direction of the points P-OP '. Tier ^ output of the narrow band filter 27 is passed to the amplifier and detector 23, which receives the alternating

009832/0078

1U9047

Voltage signal is demodulated and converted to an input of the summing amplifier 32 forwards. The one from that Detector 23 outgoing output voltage corresponds to the distance L.

The detector output is also passed to a differentiator circuit consisting of inventory 55 and differentiator 34-. The output of the differentiator circuit is a voltage which corresponds to the speed V of the train. The output of the summing amplifier 52 is connected to the amplitude comparator 35.

The comparator receives a further voltage from a reference voltage source 36 in order to compare this with the output from the summing amplifier 32. The output of the comparator 35 is routed to the relay amplifier 37, the output of which is divided by the slow and fast responding circuit at 38 and 59 into "Warn ¹¹ and ⁿ self-monitoring" components. Actuate the outputs from the slow and fast responding circuits Corresponding Belais 41 and 42 for warning and self-monitoring. One of the two inputs to amplifier 32 corresponds to the distance L between the train and the feed points PP ^ and the other * is used to derive the first propor-

009832/0076

■ * - 16 -

tional and therefore corresponds to the train speed · The output of the summing amplifier can be given by the formula

(3) - ( ^L ♦ ■ E -§— \ - - f (t)

are reproduced in which

K is the product of the hate factor for the Differentiator and the ratio of the input resistance of the summing amplifier for the distance signal to which is for the speed signal

The negative sign at the beginning is the result of the Inversion in the summing amplifier * and is approaching train negative · For example, if you have a Warning time of 30 seconds. want to have, then K «3P is set, where the following equation results

fr) - h + 3 ° - $ -) - ■■ * w

If you now consider a train at the distance L, which is greater than 30 dL / dt, under these conditions f (t) will be negative and the train will be more than 30 eec. need to get to the feed point (PP ·) » If the train is traveling at constant speed, there is a point in time ^ at which L ■ equals 30 dL / dt and f (t) will be 0. At this distance the train - if it does not change its speed - reaches the βρ 1-

009632/0078

solution point in exactly 350 sec. A short time afterwards the instantaneous value of L must be less than 30 dL / dt and f (t) thus positive Since the amplitude comparator 35 f (t) monitors, "it causes the warning relay 41 via the relay amplifier 37 and the slowly responding circuit 38 is excited when f (t) is negative · On the other hand

the relay 41 is de-energized when f (t) is 0 or positive.

Having described the basic components of the warning system the self-monitoring part of the device will now be considered in more detail.

The self-monitoring includes a self-monitoring signal that is routed to the rail track and itself changes in amplitude at a very high rate. This signal that is superimposed on the transmitted current is picked up by a holding circuit and used to drive it. This self-monitoring works when there is no train on the line, every 5 see » It takes 1.5 seconds to run the self-monitoring cycle. needed} · Should for some reason the self-monitoring cycle are not completed, then this holding circuit fails and the warning lights are activated To indicate that the device is working properly suitable indicator lights can be provided.

H490 4 7

During the self-monitoring cycle, the scaling factor for the differentiator (34) is adjusted to an appropriate one Value switched over, which with a suitable setting of the percent modulation yields a solution to the prediction equation such that during the self-monitoring cycle f (t) «" O. This is determined by the amplitude comparator 35 detected, which causes the self-monitoring relay 42 from the relay amplifier 37 and the fast-responding circuit 39 is energized · The self-monitoring relay 42 is from a slow-releasing Type (or it is with the help of further auxiliary circuits so designed) that remains aroused a little longer than the period between self-monitoring cycles. The slow response circuit 38 between the Relay amplifier 37 and the Wararelals 41 prevented j that the warning relay 41 to the self-monitoring solution the goal prediction equation addresses. · ..

The amplitude discriminator 43 monitors the distance corresponding output of the phase detector 23 and excited via the relay amplifier? 45 the relay 44 for the minimum distance, if the distance is up to Zug L is greater than the value represented by the setting at the 'reference voltage source 46' «The time * - ' pulse generator 54 triggers the self-monitoring cycles mii;

HA90A7

an optimal repetition speed. This speed must be small enough that between the Self-monitoring cycles provide enough time for prediction the train arrival time remains. The repetition speed must also be large enough that between the self-monitoring cycles a sufficiently short * time remains, which results in a reasonably short examination time for a condition that is incorrect work of the warning system. The timing pulse generator 54 controls the Lodulator 25 to which the output of the des Phase shift network 22 is conducted. The output of the modulator 25 is a carrier voltage with the Oscillator frequency that is amplitude modulated by the self-monitoring wave at the times that are passed by the time pulse generator are determined.

As mentioned earlier, this is the modulated self-monitoring wave train designed to correspond to a train at high speed so that the self-supervision response of the system only to a relatively small extent from an actual train on the Route is affected. Different waveforms can be used. Preferably, however those that lead to a signal about a rapidly changing speed are used as this gives the best results such a waveform

009832/0076 _BÄD original

1443047

fext with a modulation factor of 10 % a speed signal that increases linearly from 0 to 240 m / sec (800 feet per lake) during the one-second long self-crossing (assuming a boat length of 1.2 km ( 4000 feet) * This can be repeated every 5 seconds. The corresponding amplifier output can be displayed during the self-monitoring cycles

^through / "γ t - 1 see

and by e "E> j between the self-monitoring cycles" n. This waveform is shown in Fig. 8 * · '

Fig «, 7 shows the normally open contacts 4? bit 49 of the three heaters 41, 42 and 44, which are switched on in series between a power source and insehlüssöii 52 and 33 control of a relay (not shown) for the security system (barrier and / or flashing light) at the intersection · If one or more of the three relays (Waxn relals 41, self-monitoring relay 42 or minimum distance relay 44) is de-energized ₉ the power supply to the relay for the alarm system is interrupted and the alarm system begins to operate »

In the case of a free rail track, the ¹ supplies AC bridging resistor 19 between the rails

. * ■ »■■" "" - ■ -

Λ · OO9832 / O07i ^ '/ ' ^ 'V -...

■ U49047

17 to XB i »© ines distance from P and i", which is equal to t ** »* , © in © low impedance on the rail line, which corresponds to a train that is silent in the maximum distance · If no direct current circuits are used on the rail line, the Weehselstromwiderstand 19 Brahtßttek ice may be "the Selbstüberwaehungsmodulation of Sehienenstromes results Dahei? zwiseiiön like. & n feed points p-3? ^1, a voltage" the sick during a one second long Selbstübeiwaßkungszyklus very sohneil% of ££ AWF 0.9% ^ X ^ weeöJädea Zug corresponds

If the train 39 is ^generally a distance L on the track , the voltage appearing at the feed points ¥ -2 ' corresponds to a train that moves from Ii to (0.9 I »- Vt) or 0 during the typical one-second self-monitoring cycle , 9 & - V ^- ), where T is the train speed and Vt «Y, since t» is 1 see * Normally, the apparent movement of the train 29 due to the self-supervision modulation will be much greater than the actual train speed during the one second Self-monitoring cycle, and the self-monitoring response is therefore primarily determined by the self-monitoring modulation, except when the train is close to the feed points 3Ρ-Ϊ » ¹ When Jedooa the approaching Zmg 29 is close to the feed point

008832/0076

The th IMP ¹ is * tf the warning device is already switched on at the crossing and the working of the self-monitoring system is of little importance

The self-monitoring circuit ensures that the whole system is intact and that there is sufficient warning *. time is guaranteed * In a typical embodiment, the simulated train runs through the rails in 0 | 6 seconds, giving warnings να «approximately 0. g ^ see». The slowly responding circuit 38 prevents the warning device from being switched on via the seiais 41 _{during 1/4 seo f, which corresponds to the artificially generated warning time.}

5 illustrates another Ausfühi ^ uiissbeispiel the invention, between the fast response tung 39 VQO- AEE ^m 3elbstüberwachiuigsrelais 42, a comparator circuit 61 and a. The relay amplifier contains * The line 65 connects the clock generator 54 to the time comparator 61. All other blocks in FIG. 5 correspond to the same blocks in FIG manner as in Fig .1 a £ taeit <= t ^ ₄ ed <3ch with the one exception that now the ieiÄoÄ _t ^ erator 61 feestimmt _t 4p that the only during SelbstüljerwÄehungesntwOrtimpulB

U49047

time determined by the timing pulse occurs. This additional restriction in self-monitoring results in an even more reliable test of the entire warning system for the rail crossing.

Briefly, the operation of the circuit of FIG. 5 is that, first, the self-supervision cycle is initiated by the timing generator 54 * This circuit 54 calls at the time the simulated A high speed train signal is expected to effect the 1/4 second warning additional step signal. These two signals, the warning and the pulse from the time pulse circuit, must appear at the time comparator 61 at the same time. If for some reason no coincidence is achieved the warning system is activated by the self-monitoring system

Another possible modification of FIG. 1 is shown in FIG. 6, although it is not necessarily limited to the illustrated self-monitoring device. The phase shift network 22 can easily also in the reference path between the oscillator 21 and the reference input (64 ·) of the phase detector 23 instead of between the oscillator 21 and the reference input 64 of the phase detector are arranged. At this age

009832/0076

native arrangement, the phase shift is equal to the made in the signal path so that it is not directed equally and oppositely *. ■ ''

An embodiment of the invention, the screen, suitable for protecting rail crossings in which trains from both sides approach central feed points, is shown schematically in FIG. The mode of operation of this system corresponds to that of FIG. 1 'with the exception that, because of the lack of isolated connections, precautions had to be taken to ensure that both the left and right rails ^{can be checked from the feed points PP 1.} This will be done by the addition of the flip-flop 65. »- two relay amplifiers 66 and 67 and two relays 68 and 69, the contacts 71 and 72 of which alternate with the alternating current resistors 73 and 74 - at the left and right end of the track for the duration switch on the corresponding self-monitoring cycles

Although the main task of monitoring the rail intersections the detection of movement on the rails is * is it also necessary to secure the intersection when the train stands on the intersection and doesn't move * This would previously by means of an "Island" or "Street" circuit

0 08832/0076

H49047

However, the device of the present invention has the merit that it can meet this requirement by means of the remote voltage. As long as the distance voltage E «is greater than a predetermined value, the system works as a function of a movement. However, if the voltage E ^ corresponds to a distance smaller than this predetermined value, the system offers protection independent of the movement. "Minimum distance" called and can be set in an embodiment from 12 to 150 m (40 to 500 3 ¹ UB) on a 1.2 km (4000 I ¹ UB) long distance «With shorter distances it is less · *

The self-monitoring speaks to broken rails, open rail connections and failure of the system components at·

The two monitoring devices required to protect a single lane crossing each have three control contacts, which are »like Fig. 7 seigt, with the crossing relay are connected in series » These contacts are the minimum distance 47, the self-exercise 48 and the warning or forecast time Each of these three contacts (47 to 49) can operate

009132/0076

26- ■ '. -: - - ■ - .. ■ "■

switch on the warning device at the intersection. How one can easily see »a warning system according to the invention is therefore significantly more effective against the occurrence of Errors secured and any failure immediately activates the intersection warning system

After the essential new features of the invention have been described on the basis of preferred exemplary embodiments should be emphasized that from Various modifications and changes in the form and details of the devices shown are skilled in the art and their mode of action can be carried out, without departing from the scope of the invention. The invention is therefore intended to be further delineated by the appended claims.

009332/3073

Claims (1)

1U9047 Claims «Β« S SC S = 1 · Self-timing device for an analog computing circuit with an AC voltage input which is normally variable in a predetermined range, characterized by a clock generator for generating timing pulses; a connected to this clock and responsive to the timing pulses modulator (25) for modulating the AC voltage input at a speed or frequency that exceeds the predetermined range; first connected to the computing circuit and responsive to the output control means (39) for investigation d§r operation of the counter circuit and second nit of Bechenschaltung connected and to whose output, when the predetermined range is exceeded, responsive control devices (38), the activity of the interrupt the computing circuit. 2. Self-monitoring device according to claim 1, characterized in that the first control device ⁵⁶ 008832/007 $ if A relay amplifier (37) connected to the relay amplifier and a fast-responding relay (59t ^ 2) connected to the relay amplifier, ^A and that the second control devices comprise a slow-responding relay (38) connected to the relay amplifier (37) , 41) included. 3 · Self-monitoring device according to claim 1, characterized by one with the clock generator (54-) and the first control devices (39ι 42) connected Timing comparator (61) responsive to the timing pulses and the response of the first control device compares with the occurrence of the time control pulses in order to to check the working of the computing circuit (Pig 5) 4 «self-monitoring device according to claim 1, characterized by a differentiator (34) and with coupled to the clock (54) and the differentiator. Hate rod changing device, these scale changes respond to the timing pulse so that they change the time scale of the differentiator, whereby the differentiator is made ready to receive the modulated input. 5 · Self-monitoring device according to claim 1 for ' the use in a warning system at rail crossings, 003832/0076 1U9JH7 as characterized in that the control devices have a first, on the output of the computing circuit, if this is actuated by a signal that corresponds to an approaching train from a first sighting, responsive relay circuit (66, 68); one to the output of the computing circuit when it is approaching by a signal from an opposite sight Train is operated, responsive second relay control circuit (6 ?, 69) and with the time control devices and the first and second relay circuits connected switching devices (flip-flop) for alternating actuation of the relay circuits in dependence contained by one of the successive signals (Fig. 6). 6 · Self-monitoring device according to claim 1 for the self-monitoring of a prediction system with a first arithmetic circuit for generating a first signal representing the distance (Ejj) as a function of a variable input signal \ a second signal circuit for deriving a second signal from the first signal, which is the The instantaneous speed (Ep) corresponds to, and a third arithmetic circuit for combining the first and second signals to generate a third, representing the time of arrival 009832 / $ 007 U49047 Signals (ΈΕτ> * Ε «)» characterized by timing devices (54) for periodically supplying a simulated signal to the first arithmetic circuit *, the simulated signal being changed at a speed that exceeds the speed at which the variable input signal is normally changed Time control means and scale changing means connected to the second calculator circuit, responsive to the simulated signal and changing the page scale of the second calculator circuit, whereby the second six circuit is responsive to the simulated signal and provides a speed signal having an abnormal speed; a reference current source (46) for generating an output with a fixed amplitude} and having the reference current source (46) and the third. Computing circuit 02} connected comparison devices (55) for comparing the third signal with the output of the reference current source} in order to check the functioning of the goal prediction system *