The capacitors across the coil in a vibrator mostly suppress the arcing on the contacts and in certain types of vibrators supply the necessary energy for the armature to go through to the 'other' side. The tuning is entirely mechanical. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads