Telex ISP-100 manual Rear Panel RS-232, Connections Over 50 Feet

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Not using an RFI choke while using the front panel serial port could cause increased interference with other devices and void the FCC compliance.

RS-232 cable runs over 50 feet could cause unreliable communications. It is better to use RS-485 converters for connections over 50 feet. Be sure to read the application note on this topic before buying converters.

Figure 2-13RFI choke data.

RFI choke such as Steward PN: 28B2025-0A0 should be used at the ISP-100 end of the cable. See Figures 2-13 and 2-16, and Table 2-1 for more information.

Rear Panel RS-232

Figure 2-14RJ-45 to DB-25. Figure 2-15RJ-45 to DB-9.

The serial port selector switch should be set in the up position. If the PC’s COM port is a DB-25 connector, wire the cable according to Figure 2-14. If the PC’s COM port is a DB-9 connector, wire the cable according to Figure 2-15. No RFI choke is needed. See Figure 2-16 and Table 2-1 for more information.

Connections Over 50 Feet

The EIA specifications for RS-232 communications allow for connections up to 50 feet. For longer connections, the RS-232 signals must be converted to a standard, such as RS-485, that is tolerant of long distances. The converter on the PC end of the connection can be PC powered, but the converter at the ISP-100 end of the connection must have its own power supply. Before buying converters please contact TELEX Communications, Inc. for an application note on this topic.

Setup & Installation