The toslink connector is supplied with the Phonak TV Connector. It has a standard fiber optic connector on one end to go into the tv and a jack plug on the other (with a built in converter) that plugs into the Phonak tv device. When the tv is off the tv connector stops transmitting automatically. It just works and is of no hassle or concern. It most likely can be powered via a USB cable from the TV, but that depends on the TV.
For instance I have a Samsung Tv with several USB ports , only one of them provides power. My other TV has USB ports that all provide sufficient power, but I prefer to use the supplied power supply that came with the TV Connector