Broken wire detection within a security surveillance network

1 . An electronic communications system expander device communicatively coupled via a first differential half-duplex communications bus to and upstream from an electronic communications device, the electronic communications system expander device comprising:

a differential receiver;

an electronic processor; and

a broken wire detection circuit including a load resistor selectively connectable to an input of the broken wire detection circuit, the broken wire detection circuit being communicatively coupled at the input to the first differential half-duplex communications bus and communicatively coupled at an output to the electronic processor,

wherein the electronic processor configured to:

transmit a first message over the first differential half-duplex communications bus to the electronic communications device;

detect, at the differential receiver, a response message over the first differential half-duplex communications bus from the electronic communications device;

connect, in response to detecting the response message, the load resistor to the input of the broken wire detection circuit;

disconnect, during reception of the response message from the electronic communications device, the load resistor from the input of the broken wire detection circuit;

determine, based on a signal from the broken wire detection circuit, whether a broken wire condition exists within the first differential half-duplex communications bus; and

generate, in response to determining that the broken wire condition is present, an alert to a user.

2 . The expander device of claim 1 , wherein the electronic processor is further configured to:

detect, at the differential receiver, an end a first bit of a message from the electronic communications device;

connect, in response to detecting the end of the first bit, the load resistor of the broken wire detection circuit to the input of the broken wire detection circuit;

detect, at the differential receiver, an end of a second bit of the message from the electronic communications system expander device; and

disconnect, in response to detecting the end of the second bit, the load resistor from the input of the broken wire detection circuit.

3 . The expander device of claim 2 , wherein the signal from the broken wire detection circuit includes a signal from the load resistor corresponding to the received second bit, and wherein the electronic processor is configured to determine whether a broken wire condition is present based on a comparison between the signal from the load resistor and a received second bit of the message received at the differential receiver of the expander device from the differential half-duplex communications bus.

4 . The expander device of claim 1 , wherein the load resistor includes two resistors.

5 . The expander device of claim 1 , wherein generating the alert includes transmitting an alert notification to a control panel communicatively coupled upstream from the electronic communications system expander device via a second differential half-duplex communications bus.

6 . The expander device of claim 5 , wherein the electronic communications system expander device and the control panel are part of a security surveillance system.

7 . The expander device of claim 1 , wherein the electronic communications device is either one of another electronic communications system expander device or a peripheral device.

8 . The expander device of claim 7 , wherein the peripheral device includes at least one selected from the group consisting of a biometric sensor, an RFID tag sensor, a surveillance camera, a motion sensor, an entryway access control module, and an alarm system.

9 . An electronic communications network system including an electronic communications device and an expander device communicatively coupled via a first differential half-duplex communications bus to and upstream from the electronic communications device, the electronic communications system expander device including a differential receiver, an electronic processor, and a broken wire detection circuit including a load resistor selectively connectable to an input of the broken wire detection circuit, the broken wire detection circuit being communicatively coupled at the input to the first differential half-duplex communications bus and communicatively coupled at an output to the electronic processor, wherein the electronic processor is configured to:

transmit a first message over the first differential half-duplex communications bus to the electronic communications device;

detect, at the differential receiver, a response message over the first differential half-duplex communications bus from the electronic communications device;

connect, in response to detecting the response message, the load resistor to the input of the broken wire detection circuit;

disconnect, during reception of the response message from the electronic communications device, the load resistor from the input of the broken wire detection circuit;

determine, based on a signal from the broken wire detection circuit, whether a broken wire condition exists within the first differential half-duplex communications bus; and

generate, in response to determining that the broken wire condition is present, an alert to a user.

10 . The system of claim 9 , wherein the electronic processor is further configured to:

detect, at the differential receiver, an end a first bit of a message from the electronic communications device;

connect, in response to detecting the end of the first bit, the load resistor of the broken wire detection circuit to the input of the broken wire detection circuit;

detect, at the differential receiver, an end of a second bit of the message from the electronic communications system expander device; and

disconnect, in response to detecting the end of the second bit, the load resistor from the input of the broken wire detection circuit.

11 . The system of claim 10 , wherein the signal from the broken wire detection circuit includes a signal from the load resistor corresponding to the received second bit, and wherein the electronic processor is configured to determine whether a broken wire condition is present based on a comparison between the signal from the load resistor and a received second bit of the message received at the differential receiver of the expander device from the differential half-duplex communications bus.

12 . The system of claim 9 , wherein the load resistor includes two resistors.

13 . The system of claim 9 , wherein generating the alert includes transmitting an alert notification to a control panel communicatively coupled upstream from the electronic communications system expander device via a second differential half-duplex communications bus.

14 . The system of claim 13 , wherein the system is a security surveillance system.

15 . The system of claim 9 , wherein the electronic communications device is either one of another electronic communications system expander device or a peripheral device.

16 . The expander device of claim 15 , wherein the peripheral device includes at least one selected from the group consisting of a biometric sensor, an RFID tag sensor, a surveillance camera, a motion sensor, an entryway access control module, and an alarm system.

17 . A method of detecting a broken wire condition of a first differential half-duplex communications bus, the method comprising:

transmitting, from an electronic communications system expander device, a first message over the first differential half-duplex communications bus to an electronic communications device connected downstream from the electronic communications system expander device;

detecting, at a differential receiver of the electronic communications system expander device, a response message over the first differential half-duplex communications bus from the electronic communications device;

connecting, in response to detecting the response message, a load resistor of a broken wire detection circuit of the electronic communications system expander device to an input of the broken wire detection circuit, the broken wire detection circuit being connected to the first differential half-duplex communications bus at the input;

disconnecting, during reception of the response message from the electronic communications device, the load resistor from the input of the broken wire detection circuit;

determining, based on a signal from the broken wire detection circuit, whether a broken wire condition exists within the first differential half-duplex communications bus; and

generating, in response to determining that the broken wire condition is present, an alert to a user.

18 . The method of claim 17 , the method further comprising

detecting, at the differential receiver, an end a first bit of a message from the electronic communications device;

connecting, in response to detecting the end of the first bit, the load resistor of the broken wire detection circuit to the input of the broken wire detection circuit;

detecting, at the differential receiver, an end of a second bit of the message from the electronic communications system expander device; and

disconnecting, in response to detecting the end of the second bit, the load resistor from the input of the broken wire detection circuit.

19 . The method of claim 18 , wherein the signal from the broken wire detection circuit includes a signal from the load resistor corresponding to the received second bit, and wherein determining whether a broken wire condition is present based on a comparison between the signal from the load resistor and a received second bit of the message received at the differential receiver of the expander device from the differential half-duplex communications bus.