A hard loopback test in telco speak is a simple device that connects the transmit tip side of a circuit to the receive tip side, and the transmit ring side to the receive ring side to complete a loop where the circuit is actually sending and receiving to itself. The device is usually an RJ45x plug that a tech will modify and place into a D-mark jack. By doing this, say in a T-1 circuit, you end up with a monitoring situation where the remote end tester can send and receive patterns to check whether a circuit is taking any errors. This can also be achieved by sending a loop pattern to a piece of equipment causing it to go into a loop for testing. But the hard loop is a physical piece placed into the circuit usually where the customer plugs his equipment. Mike Q Special Equipt Installer --GTE/Verizon 30 years
No reason. It is a post-test loop.
pre-test
Loop-Back
Loop-Back
A loop back plug.
The while loop is a pre-condition loop. It tests the condition at the beginning of each loop, executes the loop if it is true, and goes back to the test after executing each iteration.
Loop-Back Plug
break
The test condition in a loop is what's used to determine when the loop should end.
A Loop-back plug.
A for loop.
The difference is that pre means before and post means after in Latin so it's tested before or after. :)