central power house (see below), via a set of self-adjusting sheaves. Each cable has six steel strands, with each strand containing 19 wires, wrapped around a sisal rope core (to allow easier gripping). The cable is coated with a synthetic lubricant to reduce wear and friction. Historically, pine tar was used to lubricate the cable. To start and stop the movement of the car, the grip operator (see below) closes and opens the grip around the cable (similar to the clutch of a conventional car). The grip's jaws exert a pressure of up to on the cable. Due to wear and tear, a grip's dies have to be replaced after three days of usage. There are four separate cables: one length and one length for the Hyde and Mason segments, a length for their common Powell section, and one length for the California Street line. Brakes Apart from the cable itself (which limits the speeds of cars when going downhill), the cable cars use three separate braking systems: Metal brake shoes on the wheels. The single-ended cars used on the Powell–Mason and Powell–Hyde lines have a foot pedal, controlled by the grip operator, that applies the brakes on the front wheels and a handle, operated by the conductor, that applies the brakes on the rear wheels. On the double-ended cars used on the California St. line, there are pedals near both grips, one controlled by the grip operator, the other by the conductor. Wooden brake blocks pressed against the track when the gripman pulls a lever. The four blocks are made of Monterey Fir and can produce a smell of burning wood when in operation. They have to be replaced after just a few days. An emergency brake consisting of a piece of steel, around 1.5 inches thick and 18 inches long, suspended beneath the car and pushed into the track slot when the gripman pulls a red lever. It wedges tightly into the slot and often has to be removed with a cutting torch. Electrical system Over the years, the cable cars have been retrofitted with several electrical components, including headlights, interior lighting, a GPS tracking system and cameras. However, unlike most modern trains, the cable cars have no method to generate power on board and instead must use large batteries that are recharged in the car barn. In 2018, the incandescent bulbs used for the headlights and interior