Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83 (MC840302); site haring.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!sdcrdcf!hplabs!hao!seismo!mcvax!turing!haring!jaap From: jaap@haring.UUCP Newsgroups: net.periphs Subject: Re: terminal noise Message-ID: <375@haring.UUCP> Date: Sun, 9-Dec-84 00:21:44 EST Article-I.D.: haring.375 Posted: Sun Dec 9 00:21:44 1984 Date-Received: Mon, 10-Dec-84 02:59:27 EST References: <36@mot.UUCP> Organization: CWI, Amsterdam Lines: 9 Apparently-To: rnews@turing.LOCAL A lot of hardware have ``switched power'' supplies. They are based on the effect that at higher frequency AC less smaller transformers are needed. Usually they bump the frequency up to 40kHz or more, however cheaper ones have lower frequencies. When the transformers are cheap as well, you and up hearing the noise made by these. It is the same effect as in cheap/old television sets (In Europe 15.625 kHz.