Method for transmitting measuring values in a fire alarm system and apparatus for the performance of the aforesaid method

• US 4,404,548 A
• Filed: 06/08/1981
• Issued: 09/13/1983
• Est. Priority Date: 06/23/1980
• Status: Expired due to Term

• Current Assignee: Cerberus ABP Investor LLC (Cerberus Capital Management LP), Zoldia Anstalt
• Original Assignee: Cerberus ABP Investor LLC (Cerberus Capital Management LP)
• Inventors: Mueller, Peter, Scheidweiler, Andreas, Muggli, Jurg, Schibli, Eugen
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US06/271,187
• Time in Patent Office: 827 Days
• Field of Search: 340/505-512, 340/518, 340/516, 340/526, 340/531, 340/536, 340/537, 340/825.05, 340/825.06, 340/825.07, 340/825.1, 340/825.12, 340/825.13 , 340/825.54, 343/6.5 R, 343/6.8 R, 179/5 R, 179/5 P
• US Class Current: 340/505
• CPC Class Codes: G08B 17/00 Fire alarms; Alarms responsive to explosion
• CPC Class Codes: G08B 26/005 with substations connected in series, e.g. cascade

Abstract

In a fire alarm system individual fire alarms are connected in series by reporting lines with a central signal station. In order to be able to connect a greater number of fire alarms with the individual reporting or signaling lines and/or in order to be able to dispatch an increased amount of current through the reporting lines, the reporting or signaling lines from the last fire alarm of a line are returned back to the central signal station in the form of a ring circuit or loop. Upon the absence of signals at a reporting line an interrogation device is reversed, so that there can be ensured that in the event of a line disturbance or breakdown of a fire alarm the remainder of the fire alarms still can be utilized for giving a signal. The individual fire alarms are structured such that during assembly the inputs and outputs can be mutually interchanged.

Claims

1. In a method of transmitting measuring values in a fire alarm installation wherein measuring values determined by individual fire alarms connected in series at alarm reporting lines are transmitted in recurrent interrogation cycles to a central signal station beginning with a fire alarm closest to the central signal station and terminating with a last fire alarm located furthest from the central signal station, the transmitted measuring values are linked at the central signal station for obtaining differentiated disturbance or alarm signals, whereby at the start of each interrogation cycle for all fire alarms there is disconnected the alarm reporting line by a voltage change, then there is again reconnected in a timewise staggered fashion the reporting lines such that each fire alarm after a certain time-delay connects a subsequently arranged fire alarm with the line voltage whereby there is caused an increase of current in the reporting line, and there is derived in an evaluation device from a number of preceding increases in the line current a momentary fire alarm address;

the improvement which comprises the steps of;

returning the alarm reporting lines from the last fire alarm in each reporting line to terminals of the central signal station; and

upon absence of fire alarm signals reversing an interrogation direction for the affected alarm reporting line.

2. The method as defined in claim 1, further including the steps of:

following the transmission of the measuring value of the last fire alarm of a reporting line feeding current into the alarm reporting lines from two different terminals of the central signal station.

3. The method as defined in claim 2, further including the steps of:

determining the time-delay by the measuring value of the fire alarm.

4. The method as defined in claim 2, wherein:

the time-delay is dependent upon the measuring value; and

the measuring value is switched-through to the central signal station within the time-delay.

5. The method as defined in claim 1, further including the steps of:

determining the time-delay by the measuring value of the fire alarm.

6. The method as defined in claim 1, wherein:

the time-delay is dependent upon the measuring value; and

the measuring value is switched-through to the central signal station within the time-delay.

7. The method as defined in claim 6, further including the steps of:

transmitting the measuring value to the central signal station in the form of a coded pulse train.

8. The method as defined in claim 6, further including the steps of:

transmitting the measuring value to the central signal station in the form of an alternating-current voltage signal at a frequency dependent upon the measuring value.

9. In an apparatus for transmitting measuring values in a fire alarm system, wherein:

fire alarms are connected in series at alarm reporting lines with a central signal station, the central signal station serves for receiving measuring values detected by individual ones of the fire alarms and transmitted to the central signal station in recurrent interrogation cycles, and wherein the central signal station further serves for linking the measuring values to obtain differentiated disturbance and alarm signals, whereby at the start of one of each said interrogation cycle all of the fire alarms are disconnected from the alarm reporting line by a change in voltage and then again connected in a timewise staggered fashion such that each alarm, after a certain time delay, connects to the line voltage a subsequently arranged fire alarm whereby there is caused an increase of current in the reporting line, an evaluation device serving to derive a momentary alarm address from a number of preceding increases in the line current, the improvement which comprises;

said individual fire alarms each possessing two inputs for the connection of the alarm reporting lines; and

each of said individual fire alarms containing time-delay circuit means which upon application of a potential at one of both inputs generates with a time-delay a signal at the other input.

10. The apparatus as defined in claim 9, further including:

a bidirectional switch provided for said time-delay circuit means.

11. The apparatus as defined in claim 10, wherein:

said bidirectional switch comprises a MOSFET transistor.

12. The apparatus as defined in claim 9, further including:

diode means for connecting the time-delay circuit means with terminals of the bidirectional switch.