Bharath, "Differential" sometimes carries several meanings, not just "current flowing in one signal has to return back through the counterpart." In many systems, differential simply means that the receiver evaluates logic levels by looking at the *difference* between two incoming signals. Such a system can benefit from immunity to common-mode noise while still using a return path other than one of the incoming signals. - Michael Mirmak Intel Corp. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Bharathkumar Raju Sent: Tuesday, January 22, 2008 4:06 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] What is meant by a differential signal Dear Members, In my understanding unlike ethernet signals (Tx+ & Tx- and Rx+ & Rx-) which are true differntial the USB signals are not true differential.=20 Differential means current flowing in one signal has to return back through the counterpart. In the ethernet protocol Tx+ current will return through Tx- and vice versa. The same holds good for Rx pair also. In an ideal differential system current flowing through the midpoint (ground) will be zero. =20 This is not the case for USB protocol. Here ground is the datum through which the return current flows and under no circumstances the ground current will be zero. Then why USB is identifed as a differential system?=20 Bharath Unlimited freedom, unlimited storage. Get it now, on http://help.yahoo.com/l/in/yahoo/mail/yahoomail/tools/tools-08.html/ ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu