CAB-E1-RJ45BNC= 10 foot Cisco Compatible equv E1 unbalanced cable. This cable consist of a single RJ45 male connector to dual BNC male connectors. CAB-E1-RJ45BNC cables are typically used to connect DS3 or T3 WAN connections to a router on your local side.
Typical Cisco Compatible cards used to interface with would be the PA-T3, PA-MC-T3, PA-T3+, PA-2T3, PA-2T3+, NM-1A-T3, and NM-1E/T3. The telco provider will typically terminate to an RJ-45 jack at the wall. This cable converts the RJ45 to dual bayonet style BNC connectors that twist and lock with a quarter turn."