Johnson Controls 300 Series Manual page 32

32 Network Control Module 300 Series Technical Bulletin
RS-232 Ports (2 and 3)
The RS-232C ports provide input/output at standard RS-232C levels
using the DTE protocol.
The user connects a cable with a DB9 Female connector onto the
NCM (detailed pinouts follow for each device).
All RS-232 connections to third-party equipment must be made with
shielded cable.
As a condition for meeting European Emissions requirements, and
being able to apply the CE Mark, we are required to use a ferrite clamp
(supplied with every NCM311) if an RS232 cable is used on Serial
Port 2. Figure 8 shows how to attach the ferrite clamp.
Mount the ferrite clamp on the serial cable as closely as possible to the
9-pin IBM® serial port connector. It can be held in place by a cable tie
mounted directly behind the ferrite clamp.