Patent US 4,207,441

An equipment is described using n electrode sets implanted in the cochlea at n different locations for allowing the brain to identify n different frequencies. A receiver implant is coupled to the electrode sets through a selector and an external emitter is coupled to a single receiver coil of the implant by means of a single emitter coil. In the emitter the sound information signal is processed for forming n analysis signals of which the frequencies correspond to said n different frequencies and raster signals which are transmitted by modulating a high frequency a.c. signal. Each raster signal comprises at least n pulses of which the durations correspond to the energies to be transmitted to the n electrodes.