A Transient Voltage Suppressor or TVS is a general classification of an array of devices that are designed to react to sudden or momentary over-voltage conditions.
TVS is a fast acting component used where quick reaction time is desired. For example, System backplane communication and all the communication ports are protected via TVS.
Communication requires quick response times so that normal functioning is not disturbed. TVS are connected between earth and positive voltage line. In case of surge / high voltage,
TVS re-directs it to the system earth which is chassis ground, thereby protecting the communication ports from permanent damage.