Subspace proximity detonators were put into small bomb-like devices used by the Koinonians during the Koinonian Wars. After many years, the devices were still in working condition. Furthermore, normal tricorders could not detect them. The USS Enterprise-D's ship's archaelogist Marla Aster was killed by such a device when exploring caves on the Koinonian homeworld. (TNG: "The Bonding" )