Negative Transition Contact   

A Negative Transition Contact gives a single one-shot pulse when the bit operand it is linked to falls from ON (logic 1) to OFF (logic 0). A Positive Transition Contact gives a single one-shot pulse when the bit operand it is linked to rises from OFF (logic 0) to ON (logic 1). You can link them to any of the following bit operands:

• Memory Bit

• System Bit

• Network System Bit

• Network System Input

• Output

• Timer

A computer ON/OFF button is an example of a Negative Transition Contact. The computer is ON.

If you push the ON/OFF button in without releasing it, the computer will not shut down. But when you release the button, the system registers a change in status from ON to OFF. The computer then shuts down.

During the system scan, a Negative Transition Contact address is evaluated for a transition from ON to OFF. A transition allows power to flow through the Negative Transition Contact for one scan.

At the end of a scan, the Negative Transition Contact is reset to OFF (logic 0). The Negative Transition Contact can only be re-activated when the triggering signal again changes from ON to Off.