Path: utzoo!telecom-request Date: 7 May 91 13:10:13 GMT From: Rolf Meier Newsgroups: comp.dcom.telecom Subject: Re: 600: 600 ohm Transformer : What Does it Mean? Message-ID: Organization: Mitel. Kanata (Ontario). Canada. Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 343, Message 5 of 13 Lines: 25 In article jon_sree@world.std.com (Jon Sreekanth) writes: > In summary, what does the magic 600:600 spec mean ? Any 1:1 > transformer should be interchangeable, and line matching really means > the secondary should be terminated into the proper impedance. You are essentially correct. However, for telephony, the reference impedance is usually 600 ohms (or sometimes 900 ohms), and so you want to easily know the matching impedance. Therefore, a 1200:600 transformer is the same as a 2:1 transformer, but the former figure more easily shows that it will match 1200 ohms to 600 ohms. Also, the dc resistance of telephony transformers is around 40 ohms, which is much less significant at 600 ohms as if it was used for 8 ohms. So, another reason for using 600:600 is to indicate that it is for high impedance applications. Don't try to use it for your stereo speakers. Rolf Meier Mitel Corporation