The Oticon Opn S and Oticon Opn Play rechargeable hearing aids have a sealed battery door, so it cannot be used to turn the hearing aids on/off like hearing aids with traditional batteries.
To turn them off, hold the volume down button for 3 seconds. The LED light will flash Red and will play 4 descending tones.
To turn them back on, hold the volume down button for 2 seconds. The LED light will flash Green and the start up jingle will play.