Wire break detection in redundant communications

1. A data communications system, comprising:

a plurality of communication devices including:

a first device initiating transmission of data to a second device;

a first single data conductor communicating said data from said first device to said second device; and

a second single data conductor communicating said data from said first device to said second device;

wherein said first single data conductor and said second single data conductor are electrically coupled at said second device forming a break detection loop;

wherein said first device includes a data transmitter connected to said first single data conductor;

wherein a break detector is coupled to both said single data conductors and asserts a break signal when detecting a break in one of said data conductors;

wherein said break detector includes a test current flowing in said break detection loop wherein said break detector detects interruption of said test current due to a break in one of said single data conductors; and

wherein said break detector includes a switching device activated when a voltage difference between said first single data conductor and said second single data conductor exceeds a set threshold due to an interruption of said test current.

2. The data communication system of claim 1 wherein said data transmitter produces a voltage on said first single data conductor, and said voltage produces said test current in said break detector.

3. The data communication system of claim 2 wherein said data transmitter includes a test mode and an operational mode, said test mode producing said voltage and said operational mode transmitting said data.

4. The data communication system of claim 2 wherein said data transmitter produces said voltage while transmitting said data.

5. The data communication system of claim 1 wherein said break detector conducts, responsive to said interruption of said test current, sufficient current from said data transmitter to said second single data connector as a result of said voltage difference to allow said transmission of said data from said first device to said second device.

6. The data communication system of claim 1 wherein said switching device consists essentially of a bipolar transistor.

7. The data communication system of claim 5 wherein said switching device consists essentially of a bipolar transistor and a junction diode anti-parallel to the base-emitter junction of said bipolar transistor.

8. A data communications method, comprising:

a) initiating transmission of data from a first device to a second device;

b) communicating redundantly said data from said first device to said second device using a pair of single data conductors electrically coupled at said second device forming a break detection loop, said first device including a data transmitter connected to said first single data conductor; and

c) asserting a break signal when detecting a break in one of said data conductors by use of a break detector coupled to both said data conductors, wherein said break detector includes a test current flowing in said break detection loop wherein said break detector detects interruption of said test current due to a break in one of said single data conductors, and wherein said break detector includes a switching device activated when a voltage difference between said single data conductors exceeds a set threshold due to an interruption of said test current.

9. The data communications method of claim 8 , wherein said data transmitter produces a voltage on said one of said first single data conductors, and said voltage produces said test current in said break detector.

10. The data communications method of claim 9 , wherein said data transmitter includes a test mode and an operational mode, said test mode producing said voltage and said operational mode transmitting said data.

11. The data communications method of claim 9 , wherein said data transmitter produces said voltage while transmitting said data.

12. The data communications method of claim 8 , wherein said break detector conducts, responsive to said interruption of said test current, sufficient current from said data transmitter to another of said single data connectors as a result of said voltage difference to allow said transmission of said data from said first device to said second device.

13. The data communications method of claim 12 , wherein said switching device consists essentially of a bipolar transistor and a junction diode anti-parallel to the base-emitter junction of said bipolar transistor.

14. The data communications method of claim 8 , wherein said switching device consists essentially of a bipolar transistor.