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SCSI termination is the process of preventing the reflection of electrical signals from the ends of SCSI buses in order to ensure reliable operation. This termination is done passively via the use of various resistors connected to the signal lines at the connector end or actively through the application of a small amount of electricity. If termination is not done, the data signals themselves can reflect back from the ends of the bus and cause various anomalies in the data because of the pulse distortion or it results in outright data loss.
SCSI termination is also known as SCSI bus termination.
SCSI termination is similar to grounding, a necessary step so that the signal is not reflected back from the end of the bus. The SCSI bus is likened to a taut string in that, when one end is vibrated, it causes the vibration to travel through the string until it reaches the other end, and then because it has nowhere to go, the vibration is reflected back to the direction it came from, bouncing from end to end until all the energy is dissipated. This is the same thing that happens with the electrical pulses that go through the SCSI bus; they are reflected back from where they came if proper termination has not been observed. As would be expected, this prevents any actual data from being recognized because of the noise and interference generated.
The electrical wave has to be terminated at the physical ends of the bus, i.e., at the connectors where it meets open air. This is done by installing a terminator at the ends of the bus after all of the actual devices on the chain.
Types of termination: