Delock Isolator 1 x serial RS-232 DB9 socket to 1 x serial RS-232 DB9 plug 3 kV. RS-232 DB9 socket to RS-232 DB9 plug. This RS-232 isolator from Delock protects all connected devices such as computers, machines, controllers, and measuring instruments from electromagnetic and electrostatic discharges as well as from voltage surges. The complete galvanic isolation of the connected devices ensures continuous data transmission even in the presence of ground or mass loops. The isolator can be used as a coupling directly between two DB9 connections without the need for an additional power supply.