A drug delivery device comprising; a housing; a cylindrical member configured to be rotatably supported inside the housing, wherein the outer surface of the cylindrical member is provided with at least first and second tracks together forming an encoder, each track comprising conductive segments and non-conductive segments; and at least first and second groups of contacts configured to engage the first and second tracks respectively at predetermined intervals along the length of the track.

A drug delivery device comprising; a housing; a cylindrical member configured to be rotatably supported inside the housing, wherein the outer surface of the cylindrical member is provided with at least first and second tracks together forming an encoder, each track comprising conductive segments and non-conductive segments; and at least first and second groups of contacts configured to engage the first and second tracks respectively at predetermined intervals along the length of the track.

An apparatus comprises a housing and a plurality of electrical contacts. Each of the plurality of electrical contacts are arranged to sequentially contact a contact device as the contact device moves through the housing. The contact device comprises a first end configured to couple to a bolt, a second end opposite the first end, and a conductive region between a first insulated region and a second insulated region.