AT&T MERLIN LEGEND Installation & Maintenance Manual page 216

Installation
Attach the Direct Station Selector
The Direct Station Selector (DSS) is an optional piece of
telephone equipment. One or two DSSs can be connected to an
MLX-28D or MLX-20L telephone.
Note: Connect the DSS(s) before you install the MLX telephones.
Before installing the DSS, consider the following:
Auxiliary power is required when
an MLX telephone (with or without an MFM) has two DSSs
attached. Use a 329A power unit (must be ordered
separately).
an MLX telephone has one DSS and one MFM attached.
Use the KS22911,L2 power unit, 400B adapter, and D6AP
cord provided with the MFM.
two MLX telephones are on the same carrier, each with
one DSS attached. Use a KS22911,L2 power unit, 400B
adapter, and D6AP cord for any additional stations with
DSSs; these can be ordered separately but are also
provided with an MFM.
When additional CU carrier power is required and the system
backed up by an Uninterruptible Power Supply (UPS), the
is
Auxiliary Power Unit 9024 should also be connected to this
UPS.
The total length of cords between the KS22911,L2 or 329A
power supply and the MLX telephone can be no more than
50 feet.
Improper operation can result if the 2-foot D8AC cord
(packaged with the DSS) is replaced with a longer cord.
3-108 Telephones and Consoles