A hearing aid has a number of selectable programmes for different listening situations. An alarm is detected by an alarm controller, and an alarm message is sent to notify of the alarm. Based at least in part upon such speed and weight measurements, an electronic controller maintains or changes the speed of the conveyor belt by dictating the output of at least one motor that drives the drive pulley. The cascade bank system has a cylinder store including five or more banks. Thus, the two clamping blocks, the two links and the middle column are interconnected with each other and are moved in concert with each other, so that the distance between the two clamping blocks can be adjusted rapidly and arbitrarily, thereby facilitating the user operating the combination tool.