I can tell you that Telex takes an interesting approach with their BTR-800 wireless intercom base station: its a commercial line-lump type switch mode power supply (24Vdc 2.5A) butted right up to the rear panel of the 1RU enclosure. Its held in place with a 4-sided metal box (front, sides, top) that totally encloses the plastic case. The front of the box has a slit that the DC output cord exits from. Its pretty tidy - the power supply has the standard IEC power connector that lines up with a matching hole in the rear of the 1RU enclosure. The DC output cable has a large Ferrite bead, then solders to the main PCB. The system power switch is in series with the DC output of the supply. I'm guessing that Telex chose to enclose the whole power supply in metal to reduce RF interference within their enclosure (I did mention this is a wireless intercom system). dwayne At 01:54 PM 2/14/2008, Harold Hallikainen wrote: >It SEEMS that it should be possible to avoid all this if there were >something like the old PC power supplies that had the inlet, power switch, >etc. all enclosed in a box with just the DC outputs coming out of the box. >We'd shove the power supply up against our rear panel and have no line >connected circuitry in our product other than that "pre-approved" box. I >think this is similar to using an external low voltage power supply. -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist