Comtech EF Data SDM-9220 - Manual (Page 59)

Hardware Installation
Memotec Inc. 4-17
NOTE: Without an adaptor, the E1 port will not operate at 75 ohms.
CAUTION: The adaptor and attached BNC coaxial cables require strain relief to
ensure that they do not loosen from the digital port:
-If the unit is mounted in a rack, you must secure the cables to a side rail
using tie-wraps, or support the weight of the cables on a tray
-If the unit is on a table, you must support the weight of the cables on the
table.
The digital port can desynchronize and the unit reset if the full weight of the
BNC coaxial cables is unsupported.