loop checking is perform before cable termination..the difference between a close loop and open loop is,tha close loop has a feedback while the open loop has not.

One can close an open circuit by adding a complete loop of wire. This will allow the electricity to flow through the circuit, while electricity will not flow in an open circuit.

it is when a control loop is open and processing

The sensitivity of an open loop control system is always 1, it is due to no feedback involved in open loop.

The system without feedback is known as open loop system. The examples of the open loop system are bread toaster, oven ,washing machine. The open loop systems are inaccurate & less complex.