Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 328)

Publication AG-UM008C-EN-P - February 2005
10-8 Using Dial-up Telephone Communication
Figure 10.5 AHL Instructions Lower and Raise DTR
Peer-to-Peer
Communication Peer-to-peer communication is the simplest method. Two units
establish a telephone modem link point-to-point using DF1
full-duplex protocol. In this mode, neither unit has control over the
other, but is simply a peer. One of the units sends the command string
to a telephone modem to dial the other unit. Once the communication
has been established, then each unit can send messages back and
forth to exchange data. The unit that initiated the connection normally
hangs up the connection as well.
This configuration is an extension of peer-to-peer communication in
that it involves stations establishing point-to-point telephone modem
links using DF1 full-duplex protocol.