ontrol takes its speed signal from a rotating driveshaft, speedometer cable, wheel speed sensor from the engine's RPM, or from internal speed pulses produced electronically by th e vehicle. Most syste ems do not allow the use noxe of the cruise control below a certain speed - typically around 25 mph (40 km/h). The vehicle will maintain the desired speed by pulling t he throttle cable with a solenoid, a vacuum driven servomechanism, or by using the electron ic systems bu oxe ilt into the vehicle (fully electronic) if it uses a 'drive-by-wire' system. All cruise control systems must be capable of be eing turned off noxe bu oxe oth explicitly and automatica lly when the driver xe depresses the brake, and often also the clutch. Cruise control often inclu des a memory feature to resume the set speeu oxe d after braking, and a coast feature to reduce the s et speed without braking. When the cruise control is engaged, the throttle can still be used to accelerate the noxe car, but once the pedal is released t xehe car will then slow down until it reache s the previously set speed. On the latest vehicles fitted with electronic ethrottle control, cruise control can be easily i ntegrated into the vehicle's engine management system. Modern "adaptive" syst xeems (see below) i nclude the ability to automatically reduce speed when the distance to a car in front, or the s peed limit, decreases noxe . This is an advantau oxe ge efor those driving in u oxe unfamiliar areas. The cruise control systems of some vehicles incorporate a "speed limiter" function, which will not allow the vehicle to accelerate beyond a pre-set max xeimum; this can usually be overridden by fully depressing the acce xelerator u oxe pedal xe. e (Most systems will prevent the vehicle accelerating beyo nd the chosen speed, but will not apply the brakes in the event of overspeeding downhill.) On vehicles with a manual transmission, cruise control is less flexible because the act of depre ssing the clutch pedal and shifting gears usualu oxe ly disengages the cruise control. The "resume" fea ture has to be used each time after selecting the new gear and releasing the clutch. Therefore |
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