An Optical Version Of The Interface Is Also Available Known As "Toslink" Which Transmits The Same Data Signals As The Electrical Iec958. This Is Achieved With An Led Transmitter And An Opto-sensor As The Receiver. High Quality Optical Interfaces Offer Several Advantages In Terms Of Galvanic Isolation And Freedom From Electro-magnetic Interference - But Cheap Fibre-optic Cables Suffer From Restricted Bandwidths And High Dispersion Which Result In Severe Timing Instability And Data Errors.