PROFIBUS operates at high frequencies (up to 12 Mbaud) using a physical copper transmission medium called RS485. For this reason, every PROFIBUS copper segment requires a terminating resistor at each end called a terminator. This terminator absorbs reflections of the signal where the copper cable segment ends. Reflections are bad news because they can corrupt PROFIBUS messages and cause network trips.
The termination is made up of a three resistor circuit of specially chosen resistors that match the impedance of the PROFIBUS cable. For this circuit to work correctly, it needs to be powered with 5V which usually is supplied to the PROFIBUS Connector’s built –in terminator by the device it is connected to.
What happens if we lose power to the last device (by locking out the device) or we need to change it? This is a problem because the last device is providing power to the termination which is preventing reflections from occurring on the PROFIBUS segment, now if we lose this termination, our entire network can be jeopardised!
The solution is to insert the T1 PROFIBUS DP Active Terminator from PROFIBUS. Use of active terminators is considered best practice as they make your network more robust in the face of slave power failures, lock-outs of equipment or device maintenance. Losing one device will no longer affect the rest of your network.