velocity can be derived from the shaft 39 s 128 rotational velocity by taking into consideration the gear 124 reduction ratio for example when the shaft 128 rotates at 1 rotation per minute rpm and the gear 124 ratio is 3 1 the motor 39 s 121 speed is 3 rpm other sensing and monitoring devices may also be employed to measure the motor 39 s 121 rotational velocity fig6 shows schematically the power source 240 and energy consuming components of the dispensing unit 10 controlled by controller 132 the energy consuming components include a communication device 134 which may include without limitation rf ir and other communication types e g magnetic relay manual buttons audible commands a pumping mechanism 136 actuated by a driving mechanism having a motor and motor driver a sensing and monitoring device 138 which may include without limitation an occlusion sensor or motion sensor an indication device 140 also referred to as u201c notification device u201d which may include without limitation a buzzer or vibration alarm fig7 shows a flow chart depicting an energy supply and control of the motor 121 in practice a low price small sized power source 240 e g button battery may be used particularly a small quantity thereof to provide a dispensing unit 10 that is of miniature size and lightweight due to the small size of a button battery the electrical power output produced thereby i e current u201c i u201d and voltage u201c v u201d is substantially lower than the electrical power required for motor operation i e a condition is satisfied whereby for example a zinc air battery has a maximum power.