Kevin is right, the cisco null modem cable works. That's the light blue satin that comes with older style cisco routers.
A JACE and a PC are both DTE devices, and thus require a null modem adapter.
The pinout between the JACE and the cisco cable is slighly different (DTR/RTS and CTS/DSR swapped), but it does work . As per Dan Anderson @ Tridium, the JACE does not care about the inbound handshake lines on a serial integration. See the difference in pinout below:
JACE 4/5/XPR series
null modem cable (Tridium part # 10148)
RJ-45 /DB9
1 DTR /6 DSR
2 RTS /8 CTS
3 TXD /2 RXD
4 GND /5 GND
5 GND /1 DCD
6 RXD /3 TXD
7 CTS /7 RTS
8 DSR /4 DTR
Cisco null modem (Cisco part # 72-3383-01 or CAB-CONSOLE)
RJ-45 /DB9
1 RTS /8 CTS (request to send/clear to send)
2 DTR /6 DSR (data terminal ready/ data set ready)
3 TXD /2 RXD (transmit/receive)
4 GND /5 GND
5 GND /1 DCD
6 RXD /3 TXD (receive/transmit)
7 DSR /4 DTR (data set ready/ data terminal ready)
8 CTS /7 RTS (clear to send/request to send
This is as cheap as I've been able to find them:
http://www.routerswholesale.com/inde...&products_id=6