DE1034716B - Device for functional testing of a frequency-modulated receiving system - Google Patents

Description

GERMAN

Devices for the functional testing of frequency-modulated receiving systems are known. One Such a device is intended for attachment to the receiver part. It can thus be used both in a End station used as well as at an intermediate station will. The use of intermediate stations that are not served is of particular importance. The relay stations in frequency-modulated directional beam transmission systems are to be regarded as intermediate stations. Such intermediate stations consist of a receiver and a transmitter. The incoming Signals are fed to the receiver via receiving antennas, in an intermediate frequency position amplified and fed to a transmitter which feeds the transmitting antenna. To increase the Such intermediate stations are carried out twice in terms of transmission security. For every transmission facility two transmission units are provided on each intermediate station. The one institution is normally in operation while the other is providing a backup transmission facility. is If the facility normally in operation is disturbed, the Reserve transfer device come into operation.

In such systems it is already known to have monitoring circuits to provide a substitute signal if the output signal is missing or too small into the input of the receiver to test the functionality of the receiver. The test signal is a high-frequency voltage that corresponds to the frequency of the received signal is equivalent to. This signal must therefore be generated at the receiver by means of a special generator will. With a very high frequency on the one hand, this signal must also have a very high frequency constancy exhibit. A generator of this type requires considerable effort. This generator must also be excellently well shielded so that the small receiving voltage can be used properly Receiver can be fed.

The object of the invention is also the To monitor the operating status of the receiving system of an intermediate station and, in the event of a malfunction, to switch over on the Reserveüberüragungseinrkhtung, but with the aforementioned disadvantages the known devices are avoided. The invention relates to a device for functional testing a frequency-modulated receiving system, which is automatically controlled by a monitoring circuit known type if the output signal of the receiving system is missing or too small is that if a certain minimum amplitude is not reached, a test signal is sent to the receiver input is switched.

Facility for functional testing
a frequency-modulated receiving system

Applicant:

"Patelhold" Patentverwertungs- & Elektro-Holding Aktiengesellschaft,

Glarus (Switzerland)

Representative: Dr.-Ing. E. Sommerfeld, patent attorney,
Munich 23, Dunantstr. 6th

W. Zimmermann, Ennetbaden, Aargau (Switzerland),
has been named as the inventor

The invention consists in that the test signal is a low frequency signal through which the receiver input existing noise voltage is amplitude modulated, and that after amplification this noise voltage in the receiving system is demodulated and at the output of the receiving system its modulation signal is withdrawn again via a filter circuit and its amplitude by means of a relay circuit is monitored in such a way that when falling below a certain minimum amplitude of the Monitoring circuit is actuated, which causes the switchover to the reserve equipment.

The device consists of a first and a second relay circuit. The first A circuit known per se relates to a circuit for monitoring the signal at the receiver output. The second relay stop determines whether the drop in the receiver output voltage is due to a weakening of the received signal or a defect of the recipient. Only in the latter case does the receiver output voltage become so small that that the switching process is initiated.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing. This schematically shows the structure of the receiving system of an intermediate station of a directional beam system shown. Such stations are set up locally distributed over the route of a transmission system. Each station has two transmission facilities, one of which is normally in operation and the other is kept ready as a reserve device to be switched on automatically if necessary

809 578/320

to become. The signal to be transmitted is frequency modulated.

The high-frequency signals arrive from the antenna 1 via the receiving amplifier 2 with the first Superposition stage and the intermediate frequency amplifier 3 on the amplitude limiter 4. The amplitude limiter sender level 5 follows.

At the receiver output is used to monitor the level of the intermediate frequency signal in a known Kind on the grid circle of the limiter tube 19 the intermediate frequency signal via the coupling capacitor 34 decoupled. The diode 9 takes care of the rectification, and the filter elements 10 and 11 smooth the voltage, so that it can control the relay 13 via the amplifier tube 12. With rheostat 14 in the cathode line of the tube 12, the operating point of the tube is set so that the relay 13 drops out as soon as the level of the IF voltage at the grid circle of the limiter tube 19 is below the minimum necessary value for a normal function of the transmission decreases.

After this monitoring circuit, which is known per se, has responded, the test process becomes Control of the receiver triggered as follows.

If the receiver output voltage is too low, the switches in its rest position shown Contact 13j an LF voltage, e.g. B. 50 Hz, from the mains transformer 15 via resistor 16 on the grid circle the first HF level. The capacitor 17 is used for high-frequency grounding of the grid circuit.

The applied voltage is relatively high, about 3 volts, so that an audio frequency amplitude modulation the noise voltage takes place on the grid of the first pipe.

If the receiver does not have a fault, i.e. if the test process was only triggered by failure or reduction of the received oscillation, the noise voltage in the receiving channel is amplified and demodulated again at the grid cathode section of the tube 19 of the limiter 4. The 50 Hz audio frequency voltage thus obtained is picked up via the A resistor 31, the capacitor 32 and the relay contact 13 _H , filtered out via the selective circuit 18 tuned to 50 Hz and brought to the amplifier tube 20.

This signal is actuated via an output transformer 21 the relay 23. This keeps its contact 23j closed. This contact is in the monitoring circuit 28, which is used to switch on a backup device and, if applicable in the case of a relay station also known per se from a transmitter monitoring device Education is affected.

On the other hand, if the receiver is out of order, then this recovered 50 Hz audio frequency voltage becomes be smaller or absent at all. In this case the relay 23 drops out, and so does the contact 23j is opened. As a result, the previously switched off reserve station is switched on.

In order to create unambiguous conditions for the receiver for the test, the receiving antenna with the antenna relay 24 is switched off for a time-limited test time. This shutdown is triggered via contact 13 _m , which applies a direct voltage to the capacitor 37 and the relay winding 24. During the charging time the relay picks up and switches off the antenna of the receiver.

In normal operation, ie with the relay 13 pulled up, the second relay circuit 20, 23 receives a Haltespaonnung, which is switched from the audio frequency source via the working side of the contact 13 _r to the selective circuit 18 and the amplifier 20, so that even during normal operation of the Contact 23j is closed.

AJs relay circuits can also deviate from the illustrated embodiment, electron tubes be used.

Claims (4)

PATENT CLAIM: 1. Device for functional testing of a frequency-modulated receiving system; which is automatically controlled by a monitoring circuit of a known type (e.g. relay circuit 9, 12, 13) in the event of a missing or too small output signal from the receiving system so that a test signal (UT) is sent to the receiver input (16, 17) when a certain minimum amplitude is not reached is switched, characterized in that the test signal is a low frequency signal by which the noise voltage present at the receiver input is amplitude modulated, and that after amplification of this noise voltage in the receiving system (2, 3, 4) this is demodulated at the output of the receiving system and its modulation signal via a The filter circuit (18) is withdrawn again and its amplitude is monitored by means of a relay circuit (20, 23) in such a way that if the amplitude falls below a certain minimum, a monitoring circuit (28), which in the case of a relay station may also be influenced by a transmitter monitoring device of known design, is interrupted becomes what the switchover to the reserve equipment is effected. 2. Device according to claim 1, characterized in that by means of a relay circuit the antenna circuit is temporarily interrupted when the first relay circuit responds. 3. Device according to claim 1, characterized in that the X ^T F signal is fed directly to the monitoring relay circuit (20, 23) in normal reception instead of the receiver input. 4. Device according to claim 1, characterized in that the relay circuits are electron tube circuits be used. Considered publications:
German Patent No. 844 325;
French patent specification No. 990 550. 1 sheet of drawings © 809 578/320 7.58