Before revision: 21: Brushes and the Brush Gear, p. 313 Brush holders 400px|Compound carbon brush holder, with individual clamps and tension adjustments for each block of carbon.Hawkins Electrical Guide, Theo.
After revision: 21: Brushes and the Brush Gear, p. 313 Brush holders 400px|Compound carbon brush holder, with individual clamps and tension adjustments for each block of carbonHawkins Electrical Guide, Theo.