Dismantled vampire tap. Central metal-tipped insulated spike contacts cable core; smaller spikes contact cable shield. Note black mark on cable sheath indicating suitable location for transceiver.
A vampire tap (also called a piercing tap) is a device for physically connecting a station, typically a computer, to a network that uses 10BASE5 cabling. This device clamps onto and "bites" into the cable (hence the vampire name), inserting a probe through a hole drilled using a special tool through the outer shielding to contact the inner conductor, while other spikes bite into the outer conductor. The vampire tap usually has an integrated AUI (Attachment Unit Interface), from this a short multicore cable connects to the network card in the station.
Vampire taps allow new connections to be made on a given physical cable while the cable is in use. This allows administrators to expand bus-topology network sections without interrupting communications. Without a vampire tap, the cable has to be cut and connectors have to be attached to both ends.