# US 2013/0154613 A1 · Signaling circuit and method to detect zone status

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- Number: US 2013/0154613 A1
- Document ID: US20130154613A1
- Status: Published application
- Kind: A1
- Application number: 13/688,626
- Filed: 2012-11-29
- Published: 2013-06-20
- Earliest claimed: 2011-12-19
- Assignees: Tyco Safety Products Canada Ltd.
- Inventors: Andrei Bucsa; Stephen D. W. Fosty
- Web page: https://patentgrep.com/patent/US20130154613A1

## CPC

- G01R 23/02: Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R 19/00: Arrangements for measuring currents or voltages or for indicating presence or sign thereof (G01R5/00 takes precedence; for measuring bioelectric currents or voltages A61B5/24)
- G06F 17/00: Digital computing or data processing equipment or methods, specially adapted for specific functions (information retrieval, database structures or file system structures therefor G06F16/00)
- G08B 29/04: Monitoring of the detection circuits
- H02H 3/087: for DC applications
- H02H 3/06: with automatic reconnection
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)

## Abstract

A bi-directional current limiter may be configured to receive an AC signal and bi-directionally limit the loop current to a predetermined current value. A first and second zone may be configured in series with the AC signal and bi-directional current limiter. The first and second zone may include unidirectional current limiters to limit a unidirectional current that is proportionately less than the bi-directionally limited current. A first opto-coupler circuit (ISO1) may be configured to detect both high and low current states in the current loop circuit. Second and third opto-coupler circuits (ISO2 and ISO3) associated with the first and second zones may be configured to detect only high current states in the current loop circuit. The status of the first and second zones may then be determined by an analysis of the current level in the current loop circuit during two half cycles as determined by the various current limiters.

## Claims

### Claim 1

A current loop circuit comprising:
an AC signal generator to generate an AC signal having a positive half cycle and a negative half cycle;
a bi-directional current limiter configured to receive the AC signal and bi-directionally limit the loop current to a predetermined current value (I3);
a first zone configured to receive the AC signal, the first zone including a unidirectional current limiter to limit a unidirectional current (I1) that is proportionately less than the bi-directionally limited current I3;
a second zone configured to receive the AC signal, the second zone including a unidirectional current limiter to limit a unidirectional current (I2) that is proportionally less than the bi-directionally limited current I3;
a first opto-coupler circuit (ISO1) configured to detect both high and low current states in the current loop circuit;
a second opto-coupler circuit (ISO2) associated with the first zone and configured to detect only high current states in the current loop circuit; and
a third opto-coupler circuit (ISO3) associated with the second zone and configured to detect only high current states in the current loop circuit.

### Claim 2 (depends on 1)

The current loop circuit of claim 1, the first zone active on the positive half cycle of the generated AC signal wave and further comprising a switch (K1) to detect a zone status such that when the switch (K1) is open the loop current is I1 and ISO2 yields a status of OFF; and when the switch (K1) is closed the loop current is I3 and ISO2 yields a status of ON.

### Claim 3 (depends on 1)

The current loop circuit of claim 1, the second zone active on the negative half cycle of the generated AC signal and further comprising a switch (K2) to detect a zone status such that when the switch (K2) is open the loop current is I2 and ISO3 yields a status of OFF; and when the switch (K2) is closed the loop current is I3 and ISO3 yields a status of ON.

### Claim 4 (depends on 1)

The current loop circuit of claim 1, ISO2 and ISO3 each including an LED that emits light when a status is ON during a corresponding half cycle of the generated AC signal, the ON status known after a complete AC cycle.

### Claim 5 (depends on 1)

The current loop circuit of claim 1, ISO1 to yield a status of OFF when there is an open loop condition in the current loop.

### Claim 6 (depends on 1)

The current loop circuit of claim 1, the AC signal generator to generate the AC signal using a push-pull technique and two (2) pulse width modulation (PWM) outputs of a microcontroller in which the isolated output is the secondary coil of an isolation transformer.

### Claim 7 (depends on 1)

The current loop circuit of claim 1, wherein:
I1 is equal to I2; and
I1/I3 and I2/I3 is approximately 0.1.

### Claim 8

A method of zone signaling in an alarm system using a current loop circuit, the method comprising:
generating an AC signal wave having a positive half cycle and a negative half cycle;
limiting a loop current resulting from the generated AC signal to a value (I3) using a bi-directional current limiter;
further limiting the loop current resulting from the generated AC signal to a value (I1) using a unidirectional current limiter in a first zone or a value (I2) using a unidirectional current limiter in a second zone, I1 and I2 being proportionally less than I3;
monitoring a first opto-coupler circuit (ISO1), ISO1 to detect high or low current states for the loop current;
monitoring a second opto-coupler circuit (ISO2) associated with the first zone, ISO2 to detect only high current states during the positive half cycle of the AC signal wave; and
monitoring a third opto-coupler circuit (ISO3) associated with the second zone, ISO3 to detect only high current states during the negative half cycle of the AC signal wave.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
determining the state of a switch (K1) in the first zone such that when the switch (K1) is open the loop current is I1 and ISO2 yields a status of OFF; and when the switch (K1) is closed the loop current is I3 and ISO2 yields a status of ON during a corresponding half cycle of the generated AC signal, the ON status known after a complete AC cycle.

### Claim 10 (depends on 8)

The method of claim 8, further comprising:
determining the state of a switch (K2) in the second zone such that when the switch (K2) is open the loop current is I2 and ISO3 yields a status of OFF; and when the switch (K2) is closed the loop current is I3 and ISO3 yields a status of ON.

### Claim 11 (depends on 8)

The method of claim 8, ISO2 and ISO3 each including an LED that emits light when a status is ON during a corresponding half cycle of the generated AC signal, the ON status known after a complete AC cycle.

### Claim 12 (depends on 8)

The method of claim 8, ISO1 to yield a status of OFF when there is an open loop condition in the current loop.

### Claim 13 (depends on 8)

The method of claim 8, wherein:
I1 is equal to I2; and
I1/I3 and I2/I3 is approximately 0.1.

### Claim 14

A zone status detection circuit comprising:
an AC signal generator to generate an AC signal having a positive half cycle and a negative half cycle coupled in series with:
a first resistor having a value R2 that ensures a comfortable current for a first opto-coupler circuit (ISO1), the first opto-coupler circuit (ISO1) configured to detect current in the zone status detection circuit;
a first zone including a resistor of value R1 coupled in parallel with a first diode conductive during the positive half cycle and a first switch (K1), the first zone associated with a second opto-coupler circuit (ISO2) configured to detect a voltage on the resistor in the first zone;
a second zone including a resistor of value R1 coupled in parallel with a second diode conductive during the negative half cycle and a second switch (K2), the second zone associated with a third opto-coupler circuit (ISO3) configured to detect a voltage on the resistor in the second zone; and
a load resistor (RLOAD) set to a value to ensure there is no output on ISO2 and ISO3 when switches K1 and K2 are both open but have a pulsed output on ISO2 or ISO3 when either switch K1 or K2 is closed.