Vacuum relays are available in SPST normally open (N/O) and normally closed (N/C) models, as well as SPDT, DPDT, and 4PDT configurations. Latching relays are available in some models. These relays are available in two main configurations: ground isolated designed for hot switching, and non-isolated meant for cold switching. Ground isolated relays have their operating elements insulated from the ground plane to provide absolute voltage isolation between the housing and the high voltage contacts...up to 15,000 V peak.

Non-isolated relays have the operating coil assembly outside the vacuum for easy coil replacement, should that ever be necessary. Certain types come with refractory metal contacts which will not stick or weld if hot switched. Others have copper alloy contacts for use in circuits where current will not be interrupted by the relay contacts. This alloy offers minimum contact resistance and high current handling capability. Mounting Jennings vacuum relays is accomplished either by a threaded coil housing, a flange, or a clamp mounting. Heavier models have mounting brackets. All models may be mounted and operated in any position.