This article is from the Token Ring FAQ, by James Messer James@NetworkUptime.com with numerous contributions by others.
An IBM-type Data Connector or Universal Data Connector (IDC or UDC),
is a hermaphroditic connector (neither male nor female). These
connectors attach to each other without having a specified male or
female connector type on each end. These connectors are commonly
found on IBM Type 1 cabling, a two-pair shielded cable.
The UDC connector has the following cabling requirements:
Red - Receive + Green - Receive - Orange - Transmit + Black - Transmit -
Pin 1 - Red - Receive + Pin 5 - Black - Transmit - Pin 6 - Green - Receive - Pin 9 - Orange - Transmit +
Pin 3 - Blue/White - Transmit - Pin 4 - White/Orange - Receive + Pin 5 - Orange/White - Receive - Pin 6 - White/Blue - Transmit +
Pin 2 - Blue/White - Transmit - Pin 3 - White/Orange - Receive + Pin 4 - Orange/White - Receive - Pin 5 - White/Blue - Transmit +