System for transmitting alarm signals with a repetition

• US 5,164,704 A
• Filed: 03/14/1991
• Issued: 11/17/1992
• Est. Priority Date: 03/16/1990
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Ericsson Messaging Systems Incorporated (Telefonaktiebolaget LM Ericsson)
• Inventors: Steen, Petrus A. J., Zijlstra, Gauke K.
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US07/669,886
• Time in Patent Office: 614 Days
• Field of Search: 340/539, 340/531, 340/506, 455/9, 455/65, 455/63, 455/67
• US Class Current: 340/539.17
• CPC Class Codes: G08B 25/10 using wireless transmission systems G08B25/009 takes precedence

Abstract

System for transmitting alarm signals, comprising at least one portable transmitting unit and one central receiver, the transmitting unit comprising a control circuit which is connected to an activation device and a transmitting circuit, the control circuit activating the transmitting circuit when the activation device is energized in order to transmit an alarm signal and in order to re-activate the transmitting circuit for the re-transmission of the alarm signal after the elapse of a delay time, the delay time being different from a delay time of another transmitting unit, the transmitting unit having a memory for storing an identification code allocated to the transmitting unit, the central receiver comprising a processing system which is connected to a receiving circuit which is suitable for receiving an alarm signal and the processing circuit activating a signalling device, on receipt of an alarm signal, for the purpose of generating an attention signal, in which system the delay time is dependent on corresponding sections having different values of identification codes allocated to a predetermined group of transmitting units.

Claims

1. A system for transmitting alarm signals comprising at least one portable transmitting unit and one central receiver,

said transmitting unit comprising

an activation device,

a transmitting circuit,

a memory for storing an identification code allocated to the transmitting unit, and

a control circuit, connected to said activation device and said transmitting circuit, for activating the transmitting circuit when the activation device is energized in order to transmit an alarm signal comprising said identification code and in order to re-activate the transmitting circuit for the re-transmission of the alarm signal after the elapse of a delay time, the delay time being different from a delay time of another transmitting unit, wherein the delay time is dependent on corresponding sections of identification codes allocated to a predetermined group of transmitting units having different values and in which the delay time is zero, or at least as long as a transmission time of the alarm signal,

said central receiver comprising

a receiving circuit suitable for receiving an alarm signal,

a processing system, connected to said receiving circuit, for activating a signalling device, on receipt of an alarm signal, for the purpose of generating an attention signal.

2. A system according to claim 1, wherein least-significant sections of the identification codes of the predetermined group of transmitting units are different, wherein the delay time is dependent on the least-significant section.

3. A system according to claim 1, wherein the delay time is determined by processing the identification code with a predetermined algorithm.

4. A system according to claim 2, wherein the delay time is determined by processing the identification code with a predetermined algorithm.