Complex sentence: An idler-wheel drive is a system used to transmit the rotation of the main shaft of a motor to another rotating device, i.e. the platter of a record-reproducing turntable or the crankshaft-to-camshaft gear train of an automobile.
Split into simpler sentences: An idler-wheel drive is a system used to transmit the rotation of the main shaft of a motor to another rotating device. For example the platter of a record-reproducing turntable or the crankshaft-to-camshaft gear train of an automobile.