The /etc/uucp/Devices file must contain entries for every communications device that a particular host uses or must know about. For example, if a machine uses a US Robotics V.32bis modem as part of the PPP link, you should ensure that /etc/uucp/Devices has an entry similar to the following:
# Use these if you have a USrobotics V.32bis modem on Port B. ACUEC cua/b - 9600 usrv32bis-ec ACUEC cua/b - 19200 usrv32bis-ec ACUEC cua/b - 38400 usrv32bis-ec
Be sure that the Devices file on each PPP endpoint machine has an entry describing its modem. For more information about /etc/uucp/Devices, refer to "/etc/uucp/Devices File".