KEF Universal Wireless System (Black) (Discontinued by Manufacturer) Wireless add-on for any existing rear surround sound speaker set-up Compatible with the full range of KEF speakers but also can be used with most other brands 2.4Ghz wireless transmission technology HFADPCM (high fidelity adaptive differential pulse code modulation), along with advanced error correction technology ensures an exceptionally robust delivery of CD-quality audio AAFHSS (advanced frequency hopping spread spectrum) processor constantly monitors several channels at a time and continually switches to the strongest available