A video introduction to cochlear implants can be seen at https://www.youtube.com/watch?v=kcwatbIWpkY&feature=youtu.be
A cochlear implant completely by-passes the defunct normal hearing mechanism and stimulates the auditory nerve directly by means of an internally implanted electrode assembly.
The system has four components. An externally worn Sound Processor which captures sound and processes it into digital information which is then transmitted by the Headpiece, worn behind the ear, which transmits these digital signals across the skin on radio carrier waves to an internally implanted Receiver which conducts the electrical signals by a connecting wire through to the Electrode Assembly which has been inserted, by an operation, within the cochlea itself.
Individual implant choice is covered in Implant Choice and the different cochlear implant systems by individual manufacturers can be found in the listed manufacturer’s names.
All cochlear implant systems have the same broad characteristics and design principles and are all well engineered. Variations arise in styling, accessories and battery type. Particular differences exist in electrode design and speech processing strategies which encode the external sound frequency details into digital signals.
A comprehensive statement on Quality Standards for Cochlear Implant Services for Children and Adults , published by the British Cochlear Implant Group, can be see here.