3.5 mm TRRS (stereo-plus-mic) sockets are particularly common on recent smartphones, and have been used e.g. by Nokia since 2006; this is often compatible with standard 3.5 mm stereo headphones. 2 different forms are frequently found, both of which place left audio on the tip and right audio on the first ring (mirroring the configuration found on stereo connectors). Where they differ is in the placement of the microphone and return contacts. The first, which places the return signal on the second ring and the microphone on the sleeve, is used by Apple's iPhone line, HTC devices, latest Samsung, Nokia and Sony phones, among others. The second, which reverses these contacts, is used by older Nokia mobiles, Samsung smartphones and some Sony Ericsson phones.[13] Some computers now include a TRRS headset socket, compatible with headsets intended for smartphones. One such pin assignment, with ground on the sleeve, is standardized in OMTP[14] and has been accepted as a national Chinese standard YDT 1885-2009.