The Comtrol RocketPort is a multiport serial adapter card that exposes RS-232 ports through a proprietary 8-pin RJ45 (4J) interface module. This cable provides the straight-through wiring needed to connect a RocketPort card’s RJ45 port to a modem’s DB-25 female connector, following the Comtrol-defined RJ45 pin assignments, which differ from EIA-568 network wiring. The RJ45 interface carries the standard RS-232 asynchronous signals — TxD, RxD, RTS, CTS, DSR, DCD, and DTR — but does not support Ring Indicator on the 4J module. Signal directions are referenced from the RocketPort card (DTE).
8 pin RJ45 (8P8C) male connector to the RocketPort card
25 pin D-SUB female connector to the modem
| Description | RJ45 | D-Sub | Dir |
|---|---|---|---|
| Request To Send | 7 | 4 | OUT |
| Data Terminal Ready | 4 | 20 | OUT |
| Ground | 5 | 7 | OUT |
| Transmit Data | 3 | 2 | OUT |
| Receive Data | 2 | 3 | IN |
| Data Carrier Detect | 1 | 8 | IN |
| Data Set Ready | 6 | 6 | IN |
| Clear To Send | 8 | 5 | IN |
Notes
The RocketPort 4J RJ45 interface uses a Comtrol-proprietary pinout that is not compatible with standard Ethernet (EIA-568) wiring. Standard interface modules on RocketPort cards use female DB-25 connectors for RS-232; Quad/Octacable fanout variants use male DE-9 connectors instead and include Ring Indicator on pin 9. The RJ45 module does not support Ring Indicator.
Signals
- RTS — Request To Send; asserted by the card to indicate readiness to transmit to the modem
- DTR — Data Terminal Ready; asserted by the card to signal that it is active and ready
- GND — Signal Ground; common reference for all RS-232 signal levels
- TxD — Transmit Data; serial data sent from the RocketPort card to the modem
- RxD — Receive Data; serial data received by the card from the modem
- DCD — Data Carrier Detect; asserted by the modem when a carrier signal is detected
- DSR — Data Set Ready; asserted by the modem to indicate it is powered and ready
- CTS — Clear To Send; asserted by the modem to permit the card to transmit