Radio alarm system

Assignee: Diehl Stiftung and Co KG

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Filing: 1991-11-05

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Granted: 1997-02-26

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Expires: 2011-11-05

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Abstract

Abstract A radio alarm system is described which offers adequate protection against interference due to blocking of the radio paths and against external manipulation. For this purpose, it is proposed that each signalling unit of the alarm system transmits at least two radio signals for an alarm signal, using a different carrier frequency and being coded in identical or different fashion. The central unit accordingly receives with its receivers the at least two radio signals from each signalling unit and checks the affiliation of the signalling units transmitting the radio signals by checking the validity of the coding. It is proposed in addition that an evaluation unit be provided in the receiver unit of the central unit which identifies the field strength of each received radio signal, analyses the associated data telegrams for affiliation to the system of the signalling units transmitting them, if an invalid data telegram is detected, compares the value of the received field strength of the radio signal concerned with a predefinable minimum value and, if this minimum value is exceeded by a predefinable amount, where this amount must be exceeded for a specific time period, triggers a warning indicator. <IMAGE>

Inventors

👤 Norbert Schaaf

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-10-29 17:13

CPC Classifications

G; G08; G08B; G08B29/00; G08B29/16; G08B25/00; G08B25/01; G08B25/10; G08B26/00; G08B26/007

Claims Analysis

Total Claims: 5

Claim 1

Independent Claim 201 words

Radio alarm system, comprising a central processing unit with a receiver unit for the reception of radio signals from signalling units in the form of data telegrams, each of which represents one event, the receiver unit being tuned to the radio signals in such a way that it can only process data telegrams from signalling units belonging to the system, in order to trigger an alarm or a function, characterized in that the signalling units (1) each emit at least two radio signals for the same information, these having a different carrier frequency and being coded in data telegrams of permanently preset coding; in that, in the receiver unit of the central processing unit, an evaluating unit (26) is provided which detects the field strength of each received radio signal, analyses the associated data telegrams as to whether the signalling units transmitting them belong to the system, in the case of identifying an invalid data telegram compares the value of the received field strength of the relevant radio signal with a preset minimum value and triggers a warning display if this minimum value is exceeded by a predeterminable amount, this amount having to be exceeded for a specific period of time.

Claim 2

Dependent Claim 49 words

Radio alarm system according to Claim 1, characterized in that the evaluating unit (26) triggers an alarm when the invalidity of all the received data telegrams is detected as well as when the minimum value of the field strengths of each radio signal is exceeded by the predeterminable amount.

Claim 3

Dependent Claim 164 words

Radio alarm system according to Claim 1 or 2, characterized in that the central processing unit has in addition at least two transmitters for transmitting signals for status interrogation of each signalling unit (1); in that each signalling unit (1) respectively has at least two transmitters forming a transmitting unit (62) and at least two receivers forming a receiver unit (63) with an off the line voltage source (50) which can be connected as required by switching elements (53, 54) to its active components, the switching-on of the voltage source (50) and consequently the activation of the transmitting and receiver units (62, 63) being effected by at least one HF detector (51) connected to the aerial (55), in such a way that the transmitter energy emitted by the transmitters of the central processing unit and received by the receiver unit (63) of the signalling unit (1) changes the switching state of the HF detector which in its turn controls the switching elements (53, 54).

Claim 4

Dependent Claim 30 words

Radio alarm system according to Claim 3, characterized in that a dynamizing element (75) is connected between the aerial (55) of the signalling unit (1) and the HF detector (51).

Claim 5

Dependent Claim 77 words

Radio alarm system according to one of Claims 1 to 4, characterized by two threshold-value comparators, which compare the supply voltage of the signalling units with two different threshold values, the signalling unit transmitting a first radio signal to the central processing unit if the voltage falls short of one higher threshold value and a second radio signal triggering an alarm or preventing live-switching of the system if it falls short of the second lower threshold value.

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