S/PDIF is an acronym for Sony/Philips Digital Interconnect Format.
This is a multichannel, single connection digital protocol with two standards – Professional and Consumer.
Please refer to the user guide to see which standard is used for your A&H product.
More information can be found online:
http://en.wikipedia.org/wiki/S/PDIF
http://www.sweetwater.com/insync/pro-consumer-s-pdif-standards-explained