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 (e.g. a computer or printer) to a network that uses 10BASE5 cabling. This device clamps onto and "bites" into the cable (hence the vampire name), forcing a spike through a hole drilled through the outer shielding to contact the inner conductor while other spikes bite into the outer conductor. From the vampire tap, a short cable called an AUI (Attachment Unit Interface) is connected directly from the tap to the network card in the PC. 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.
Vampire taps may also be used for malicious purposes such as transparent network monitoring.