Overview

The board uses transient voltage suppressors to clamp fast rising signals levels above 12 volts and below -7 volts to earth ground. Larger disturbances may cause the gas tubes to fire in addition to the transient suppressors. If the disturbance energy level is sufficient, the in line fuses will open, isolating the equipment from the communications lines. Extremely large disturbances may actually destroy the circuit board, in the process of minimizing damage to the device it connects to the communications lines. There are protection devices for 2 separate communications pairs. The signal ground termination allows different ground levels to tie together with 100 Ohm resistors when there is a large difference in ground potential. It can be used on all nodes in a RS-485 communications network. Two wire networks can use either pair.