BOX COUPLERS are predominately utilized in laboratory applications. 

ESI-210
Two Stub Box Coupler - BJ77 (3 lug) Connector
ESI-210 datasheet
ESI-2210
Two Stub Box Coupler - terminated on one side
ESI-2210
ESI-211
Two Stub Box Coupler - internally terminated
ESI-211
ESI-212
Two Stub Box Coupler - for H009 bus
ESI-212
ESI-2310
Two Stub Box Coupler - internally terminated
ESI-2310
ESI-220
Two Stub Box Coupler - BJ377 Threaded Connector
ESI-220
ESI-2220
Two Stub Box Coupler - BJ377 Threaded Connector terminated
ESI-2220
ESI-230
Two Stub Box Coupler - BJ157 Connector
ESI-230
ESI-240
Two Stub Box Coupler - BJ3157 Connector
ESI-240
Internally Terminated
Other internally terminated 2 stub couplers
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ESI-2310R27
Two Stub Internally Terminated Bus Coupler that can be Switched out of the Circuit to Accommodate Testing.
ESI-2310R27