master vibrator

from The Collaborative International Dictionary of English v.0.48
Master vibrator \Mas"ter vi"bra*tor\
   In an internal-combustion engine with two or more cylinders,
   an induction coil and vibrator placed in the circuit between
   the battery or magneto and the coils for the different
   cylinders, which are used without vibrators of their own.
   [Webster 1913 Suppl.]
    

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