I haven't been following this thread, but if anyone's interested in temperature control techniques of about 50 years ago, see http://kauko.hallikainen.org/hi/brochures/ . Harold -- FCC Rules Updated Daily at http://www.hallikainen.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist