Described is a cartridge (200) comprising a body (205) adapted to contain a medicament, a bung (210) slidably disposed in the body (205) and having a distal face (215) and a proximal face (220), and a light element (225) coupled to a component of the cartridge (200). Further described is a medicament delivery device (100) comprising the cartridge (200), a first receiver (110) adapted to receive an optical signal from the light element (225) and convert the optical signal into a first electrical signal, and a second receiver (115) adapted to receive an optical signal from the light element (225) and convert the optical signal into a second electrical signal.
