Return-Path: Received: (qmail 21602 invoked from network); 14 Jun 2000 11:45:11 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by bells.core.plus.net.uk with SMTP; 14 Jun 2000 11:45:11 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 132BV7-00029j-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 14 Jun 2000 12:38:29 +0100 Received: from helios.herts.ac.uk ([147.197.200.2]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 132BV6-00029e-00 for rsgb_lf_group@blacksheep.org; Wed, 14 Jun 2000 12:38:28 +0100 X-Priority: 3 X-MSMail-Priority: Normal Received: from [147.197.200.44] (helo=gemini) by helios.herts.ac.uk with esmtp (Exim 3.11 #1) id 132BUw-0003gz-00 for rsgb_lf_group@blacksheep.org; Wed, 14 Jun 2000 12:38:18 +0100 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: <9179.200006141138@gemini> From: "James Moritz" Organization: University of Hertfordshire To: rsgb_lf_group@blacksheep.org Date: Wed, 14 Jun 2000 12:45:33 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 8bit Subject: LF: LF crystals X-Mailer: Pegasus Mail for Win32 (v3.11) Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Dear LF group, Looking through my box of crystals recently, I found some operating in the range 30 - 40kHz. They are in glass envelopes, and I noticed that the metalisation on each side of the quartz plate is divided into two halves, giving four electrodes. On some units, all four electrodes are connected to seperate pins, while on others two diagonally oposite electrodes are commoned, giving only 3 external connections. They look a little like 2 pole monolithic crystal filters, but have no bandwidth marked on them, and I have not heard of such filters being used at low frequencies. Does anybody know how these 3 and 4 terminal crystals are used? Just curious really. Cheers, Jim Moritz 73 de M0BMU