AUI to thick ethernet transceiver designed to connect to network cards with an AUI 15 pin D socket. This interfaced to a 50 Ohm coaxial cable via N-type coax connectors and provided a connection “Drop”.

The correct name for this is a Medium Attachment Unit.

The transceivers are powered from a source in the network card, the tx and rx connections are over a twisted pair.

The card on the right is an old 3Com one, it has from bottom to top, a thin ethernet BNC socket (10Base-2), and AUI port for connecting to the 3C108 transceiver (Using a 15pin D plug to 15pin D socket, 3 sets of twisted pairs, Tx, Rx and power) and at the top, a 10Base-T RJ45 connector.

Two basic versions of thick ethernet taps were produced, this on is an example of where the Yellow Coax cable has to be severed and an N connector plug crimped or soldered to each end, these are then screwed in to the tap.

The other type used a sharp pin to pierce the cable and could be installed without interruption to service, these were often referred to as “Vampire Taps”.

This MAU seems to have the option to install either the N connector module or something else from the way it is constructed.