An earphone system, the system comprising: an earphone interface comprising a plurality of contacts arranged to interface with an earphone jack of an earphone, wherein the earphone interface is arranged to interface with both a type of earphone jack having three poles and a type of earphone jack having four poles; a controller comprising a plurality of ports arranged to communicate with an earphone that is operatively connected to the earphone interface via the earphone jack; and an earphone compatible circuit arranged to: control connection states between the contacts of the earphone interface and the ports of the controller according to a type of the earphone jack interfacing with the earphone interface; and connect corresponding contacts of the earphone jack to the respective ports of the controller; wherein to control the connection states between the contacts of the earphone interface and the ports of the controller the earphone compatible circuit is further arranged to: receive a first signal from a first contact of the earphone interface, wherein the first signal corresponds to a signal from a ground pole of the earphone jack or a signal from a microphone pole of the earphone jack, via the first contact of the earphone interface; receive a second signal from a second contact of the earphone interface, wherein the second signal corresponds to a signal from a ground pole of the earphone jack or a signal from a microphone pole of the earphone jack, via the second contact of the earphone interface; and determine the connection states according to an outcome of a comparison between the first signal and the second signal; wherein at least one of the first signal and the second signal corresponds to a signal from a ground pole of the earphone jack. an earphone interface comprising a plurality of contacts arranged to interface with an earphone jack of an earphone, wherein the earphone interface is arranged to interface with both a type of earphone jack having three poles and a type of earphone jack having four poles; a controller comprising a plurality of ports arranged to communicate with an earphone that is operatively connected to the earphone interface via the earphone jack; and an earphone compatible circuit arranged to: control connection states between the contacts of the earphone interface and the ports of the controller according to a type of the earphone jack interfacing with the earphone interface; and connect corresponding contacts of the earphone jack to the respective ports of the controller; control connection states between the contacts of the earphone interface and the ports of the controller according to a type of the earphone jack interfacing with the earphone interface; and connect corresponding contacts of the earphone jack to the respective ports of the controller; wherein to control the connection states between the contacts of the earphone interface and the ports of the controller the earphone compatible circuit is further arranged to: receive a first signal from a first contact of the earphone interface, wherein the first signal corresponds to a signal from a ground pole of the earphone jack or a signal from a microphone pole of the earphone jack, via the first contact of the earphone interface; receive a second signal from a second contact of the earphone interface, wherein the second signal corresponds to a signal from a ground pole of the earphone jack or a signal from a microphone pole of the earphone jack, via the second contact of the earphone interface; and determine the connection states according to an outcome of a comparison between the first signal and the second signal; wherein at least one of the first signal and the second signal corresponds to a signal from a ground pole of the earphone jack. receive a first signal from a first contact of the earphone interface, wherein the first signal corresponds to a signal from a ground pole of the earphone jack or a signal from a microphone pole of the earphone jack, via the first contact of the earphone interface; receive a second signal from a second contact of the earphone interface, wherein the second signal corresponds to a signal from a ground pole of the earphone jack or a signal from a microphone pole of the earphone jack, via the second contact of the earphone interface; and determine the connection states according to an outcome of a comparison between the first signal and the second signal; wherein at least one of the first signal and the second signal corresponds to a signal from a ground pole of the earphone jack.