System and method for loop diagnostics in a security system

• US 6,696,940 B2
• Filed: 11/29/2001
• Issued: 02/24/2004
• Est. Priority Date: 11/29/2001
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Marino, Francis C., Li, Tony Tung Sing
• Primary Examiner(s): POPE, DARYL C
• Application Number:
  US09/996,492
• Publication Number:
  US 20030101352A1
• Time in Patent Office: 817 Days
• Field of Search: 340/506, 340/508, 340/514, 340/511, 340/533, 340/286.02, 340/3.1, 307/10.1
• US Class Current: 340/511
• CPC Class Codes: G08B 29/06 Monitoring of the line circuits, e.g. signalling of line faults

Abstract

A security system comprising a control panel and a plurality of individually-addressable security system modules connected to the control panel on a loop data bus. Each of the security system modules has a reference generating means for generating a variable reference voltage signal, which is controlled by control data received from the control panel. Each module also has means for selecting a loop input signal for analysis from a plurality of available loop input signals, and comparing means for comparing the selected loop input signal to the reference voltage signal. The comparing means generates an output signal when the selected loop input signal exceeds the reference voltage signal. The modules also have means for indicating to the control panel via the loop data bus the state of the reference generating means when the comparing means generates an output signal, whereby the control panel can determine the value of the selected loop input signal.

Claims

1. A security system comprising:

a control panel;

a plurality of individually-addressable security system modules connected to the control panel on a loop data bus;

each of said modules comprising;

reference generating means for generating an incrementally increasing reference voltage signal, said means being controlled by control data received from the control panel;

means for selecting a loop input signal for analysis from a plurality of available loop input signals;

comparing means for comparing the selected loop input signal to the reference voltage signal, said comparing means generating an output signal when the selected loop input signal is exceeded by the incrementally increasing reference voltage signal;

means for indicating to the control panel via the loop data bus the state of the reference generating means when the comparing means generates an output signal;

whereby the control panel can determine the value of the selected loop input signal.

2. The security system of claim 1 wherein said reference generating means comprises

a counter comprising a clock input for incrementing said counter and a plurality of output bits, said clock input configured to receive said control data from said control panel;

a digital-to-analog converter comprising a plurality of input bits and an analog output for generating said variable reference voltage signal, said input bits coupled to said output bits of said counter;

whereby, when said control data comprises a bit stream input to said counter, said counter will generate a reference voltage signal that increases as the number of clock pulses input to said counter increases.

3. The security system of claim 2 wherein said means for selecting a loop input signal for analysis from a plurality of available loop input signals comprises a plurality of transistors, each of said transistors configured to switch a corresponding one of said loop input signals in accordance with a multiple-bit input selection command word received from said control panel.

4. The security system of claim 3 wherein said control panel transmits a serial control word comprising the input selection command word and the control data, wherein the control data comprises a plurality of serial clock pulses.

5. The security system of claim 4 wherein said means for indicating to the control panel via the loop data bus the state of the reference generating means when the comparing means generates an output signal comprises means for suppressing the signal line comprising said serial clock pulses;

whereby the control panel is able to determine the counter value at which the comparing means generates an output signal by analyzing the number of serial clock pulses that were sent to the module before the signal line comprising said serial clock pulses is suppressed.

6. The security system of claim 5 wherein the counter value is used by the control panel to determine the relative voltage of the selected input with respect to a loop voltage applied to the module.

7. The security system of claim 5 wherein the counter value is used by the control panel to determine the actual loop voltage applied to the module by selecting a known reference voltage for comparison to the loop vooltage by the control.

8. In a security system comprising a control panel and a plurality of individually-addressable security system modules connected to the control panel on a loop data bus;

a method of testing the security system comprising the steps of;

transmitting control data from the control panel to an addressed one of said modules over the data bus;

generating at the addressed module an incrementally increasing reference voltage signal controlled by the control data received from the control panel;

selecting at the addressed module, as a function of the control data, a loop input signal for analysis from a plurality of available loop input signals;

comparing the selected loop input signal to the reference voltage signal;

generating an output signal when the selected loop input signal is exceeded by the incrementally increasing reference voltage signal;

indicating to the control panel via the loop data bus the state of the reference generating means when the output signal is generated;

whereby the control panel can determine the value of the selected loop input signal.

9. The method of claim 8 wherein said step of generating an incrementally increasing reference voltage signal comprises the steps of:

inputting said control data as a clock signal into a counter;

coupling output bits of the counter to corresponding input bits on a digital-to-analog converter;

generating a reference voltage signal from the output of the digital to analog converter that increases as the number of clock pulses input to said counter increases.

10. The method of claim 9 wherein said step of selecting a loop input signal for analysis from a plurality of available loop input signals comprises the step of controlling a plurality of transistors in accordance with a multiple-bit input selection command word received from said control panel, each of said transistors configured to switch a corresponding one of said loop input signals.

11. The method of claim 10 wherein said control panel transmits a serial control word comprising the input selection command word and the control data, wherein the control data comprises a plurality of serial clock pulses.

12. The method of claim 11 wherein said step of indicating to the control panel via the loop data bus the state of the reference generating means when the output signal is generated comprises the step of for suppressing the signal line comprising said serial clock pulses;

whereby the control panel is able to determine the counter value at which the comparing means generates an output signal by analyzing the number of serial clock pulses that were sent to the module before the signal line comprising said serial clock pulses is suppressed.

13. The method of claim 12 wherein the counter value is used by the control panel to determine the relative voltage of the selected input with respect to a loop voltage applied to the module.

14. The method of claim 12 wherein the counter value is used by the control panel to determine the actual loop voltage applied to the module by selecting a known reference voltage for comparison to the loop voltage by the control.