That is slightly incorrect as the landing gear was either raised or lowered by unlocking a lever from a gate and then moving it to the up or down position. After the landing gear had either raised or lowered the lever would automatically move to the locked position, it was not a push button. There was also a CO2 emergency system that would lower the undercarriage if the hydraulics failed.
There would often be a horn on early models that would sound if the throttle was closed too far if the wheels were not down.
