This is for connection of a computer that is running Alarmware™ configuration software. The connection would be made in order to allow transfer of configuration programming, including voice messages, between the Catalyst and the portable computer.
The cable required for this is a generic standard "PC to PC" "Null Modem" serial cable, (sometimes called a Laplink™ cable). The cable has female 9 pin D-Sub connectors on both ends. The connection port on the Catalyst is Port 3, the 9-pin connector nearest the Telephone Jack port.
Refer to the Cable Diagram and Bottom End Connector View Diagram.