Fail-safe microprocessor-based control and monitoring of electrical devices

A fail-safe system for monitoring at least one device, said fail-safe system comprising, for each such device:

• at most two pairs of positive and negative output points connected to input signals to the device;
• at most two pairs of positive and negative input points connected to receive signals from the device;
• and
• a processor, operating using a program, for generating a primary code comprising a series of three-state digits, each of said digits having a state selected from the group consisting of a first state corresponding to a direct current pulse of positive polarity, a second state corresponding to a direct current pulse of negative polarity and a third state corresponding to an absence of both the direct current pulse of positive polarity and the direct current pulse of negative polarity, said primary code comprising at least one digit having the first state and one digit having the second state,
• said processor further being for applying the primary code to said output points and for detecting a first response signal at said input points,
• said processor further being for comparing the first response signal with the primary code to detect an active state of the device.

A fail-safe system for controlling at least one device, the device being of a type having at least a first terminal and a second terminal and having a safe state that is an off state of the device, said fail-safe system comprising, for each such device:

• first control circuitry comprising at least one independent positive control circuit for the first terminal of the device;
• second control circuitry comprising at least one independent negative control circuit for the second terminal of the device, said first and second control circuitry together comprising at most a pair of independent positive and negative control circuits for each of the first and second terminals of the device,
• where each said positive control circuit comprises at least one positive energy output point for outputting positive energy to a respective terminal of the device and two positive energy input points for inputting positive energy from a respective terminal of the device, and each said negative control circuit comprises at least one negative energy output point for outputting negative energy to a respective terminal of the device and two negative energy input points for inputting negative energy from a respective terminal of the device;
• and
• means for causing the device to attain its off state through an independent removal of either the positive or negative energy from the device.

A fail-safe system for controlling at least one device, the device being of a type having at least a first terminal and a second terminal and having a safe state that is an on state of the device, said fail-safe system comprising, for each such device:

• first control circuitry comprising at least one independent positive control circuit for the first terminal of the device;
• second control circuitry comprising at least one independent negative control circuit for the second terminal of the device,
• where each said positive control circuit comprises at least one positive energy output point for outputting positive energy to a respective terminal of the device and two positive energy input points for inputting positive energy from a respective terminal of the device, and each said negative control circuit comprises at least one negative energy output point for outputting negative energy to a respective terminal of the device and two negative energy input points for inputting negative energy from a respective terminal of the device;
• and
• means for causing the device to attain its on state through an independent application of both the positive and negative energy to the device.