Black Box 3600 User Manual page 36

Installation
Leased Line Connection (TELSET/LEASED LINE Jack)
Private or leased lines use four-wire or two-wire lines. In this mode, the
user configures the unit for four-wire or two-wire operation, depending
on the private line service used.
The telephone company will install the leased line and wall jack at your
site. The line connects to the modem at the 8-position TELSET/
LEASED LINE jack.
Figure 2-4 shows a typical modem hookup for operation over private
leased lines with dial backup.
2-8 Modem 3600