Model 232SP9 protects RS-232 ports from damage caused by large voltage peaks from lightning and other power problems. The surge protector uses 600W Transient Voltage Suppressors to protect all 9 pins. It has one DB9 male and one DB9 female connector with all 9 pins passing straight through. The TVSs are connected between the ground screw and pins 1, 2, 3, 4, 5, 6, 7, 8 and 9. The 232SP9 will suppress any voltage levels above 12 Volts without affecting the normal RS-232 data.

The 232SP9 is placed inline, between the data cable and the RS-232 port, as close to the protected port as possible. The ground screw must be connected to earth ground. A minimum of 12 AWG copper wire is recommended. Model CU15B is 1.5 x 0.016 in (38 x 0.25 mm) copper cut to length for ground connections that are longer than a few feet (one meter). If this device is not properly grounded it will not protect RS-232 lines.