AT&T Merlin II Feature Module 2 Data Communications Manual page 47

MPDM Option Switches
FIGURE 3-8 MPDM and RS-232-C interface option switch settings.
3-10 Local Host Computer Access
MPDW
Facaplate
The MPDM faceplate has two Dual In-line Package (DIP) option switches, one
with 10 positions and the other with 12 position-as seen in Figure 3-8. In
addition, the RS-232-C Data Interface Circuit Pack has an 8-position DIP
option switch.
The documentation that came with your MPDMs discusses the function of
each switch setting. Follow the suggestions below to set switches unless the
computer or data terminal to which the data modules connect has different
requirements.
All option switches on the RS-232-C Data Interface Circuit
NOTE:
Pack should be off unless the data device to be connected requires a
specific lead.