Not quite true Jack,
When the landing gear is commanded down by the crew, the uplock hook for each gear is unlocked by hydraulic pressure. Once the hook is released , the gear is driven down and aft by springs, hydraulic actuators, aerodynamic forces and gravity. The doors freefall open when unlocked , sometimes aided by the wheels and tyres pushing on them. The landing gear reach the full-down and extended position within 10 seconds and are locked in position by spring-loaded downlock bungees. If hydraulic pressue is not available to release the the uplock, a pyrotechnic iniator at each landing gear uplock hook automatically releases the uplock hook on each gear one second after the crew has commanded the gear down. The landing gear is deployed at approx 300feet AGL.