In a 1+1 HSB configuration, the communication path between the main (active) and spare (standby) MPR-e radios installed on a tower is set up using a tight cable.
A tight cable is required with MPT-HC V2, MPT-XP, MPT-HLC, MPT-HLC plus, and MPT-QAM radios (1+ 1 HSB is not supported on MPT-MC radios).