A transmission belt is a Leninist concept developed to create a figurative model of the relationship between Bolshevik vanguard party, the mass of the proletariat, and from the mass of working people as a whole.
Origins
Lenin introduced the concept in a speech addressed to a Joint Meeting Of Communist Delegates To The Eighth Congress of Soviets, Communist Members Of The All-Russia Central Council Of Trade Unions And Communist Members Of The Moscow City Council Of Trade Unions, on 30 December 1920.
References
Transmission belt Wikipedia(Text) CC BY-SA