Rockwell Automation 1746-BAS-T SLC 500 Basic Basic-T Modules - Manual (Page 34)

Publication 1746-UM004B-EN-P - December 2005
2-8 Component Selection
Leased Phone Line
A leased phone line is a private, dedicated phone line. Leased phone
lines provide a phone link between modems that is available for
communication at all times. Typically, leased phone lines are used
when you have a high or constant transfer of communication between
the module and external devices.
Radio Link
A radio link provides a communication link when phone lines are
inaccessible or expensive to use. A radio link provides a
communications link between radio modems.
Dial-Up Modem
Dial-up or phone modems are modems capable of communicating
across standard phone lines. One dial-up modem initiates the
communication, while another modem receives the communication.