/sys$common/syshlp/helplib.hlb TELNET, Qualifiers, /BIND_SESSION  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BIND_SESSION network_device

    Optional. Default: None.

    Binds a TELNET terminal device to an existing network device. If
    the bind is successful, the DCL symbol $TELNET_DEVICE contains
    the TNA device name.