Extended insulation on the center contact supports the 500 V rating, giving extra creepage for RF power monitoring or test equipment where the signal rides on a DC bias.
What the 500 Mating Cycles and Temperature Range Mean for Field Duty
The PTFE dielectric inside the BNC supports that wide range without dielectric creep.
Sourcing This Obsolete BNC Jack
The 227716-3 is listed as Obsolete in the TE Connectivity lifecycle.
