---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Tue 03/24/09: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:26 PM - isolation circuit (jamesneely) 2. 03:48 PM - Re: isolation circuit (Doug McNutt) ________________________________ Message 1 _____________________________________ Time: 02:26:48 PM PST US Subject: Avionics-List: isolation circuit From: "jamesneely" (Please excuse the double post. I also posted this on the aeroelectric list) I have a flightline fl-760 and the manual says that both mikes go hot on transmit. That doesn't seem a like a great idea, particularly in a noisy cockpit. They mention an optional isolation relay board, but apparently they never did produce it, so I have to make up my own. The problem is that while I can solder just fine, I suck at designing circuits. Has anyone made one of these boards, or has a schematic that I can work from? or any source for buying such beast? Here's the diagram provided by Flightline: thanx, James Read this topic online here: http://forums.matronics.com/viewtopic.php?p=236018#236018 Attachments: http://forums.matronics.com//files/fl_760_wiring_diagram_934.jpg ________________________________ Message 2 _____________________________________ Time: 03:48:39 PM PST US From: Doug McNutt Subject: Re: Avionics-List: isolation circuit At 14:20 -0700 3/24/09, jamesneely wrote: >I have a flightline fl-760 and the manual says that both mikes go >hot on transmit. That doesn't seem a like a great idea, particularly >in a noisy cockpit. They mention an optional isolation relay board, >but apparently they never did produce it, so I have to make up my >own. >The problem is that while I can solder just fine, I suck at >designing circuits. Has anyone made one of these boards, or has a >schematic that I can work from? or any source for buying such beast? >Here's the diagram provided by Flightline: Two double pole relays suitable for the 12 or 24 volt aircraft power. Power coils from fused aircraft circuit and return the coils through the tip pins of the two push to talk jacks. Connect mike audio inputs 1 and 2 through one pair of relay contacts to the two mike audio inputs to the radio. You could use only one of the inputs but there might be a problem if both talk switches are simultaneously activated. Connect the PTT radio pin through the other relay poles so that it is grounded whenever either relay is activated. Or. . . If you use voice activated intercom those features are probably built into it. Just wire the aircraft for a single mike output from the intercom. Or. . . Some microphones, mostly older ones, use a double pole switch so that the mike audio is only present when its own talk switch is pushed. They're terrible for use with an intercom. -- --> From the U S of A, the only socialist country that refuses to admit it. <-- ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message avionics-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Avionics-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/avionics-list Browse Digests http://www.matronics.com/digest/avionics-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.