Our product has unique electronic compression depth and frequency detector.

1. First right operation: the 4 indicate light on the left shoulder will be on.
2. the lights off: lack of battery or operation mistake
3. when start the operation, yellow and green light will be off
4. red light: Press frequency 0-60 beats/min
  Yellow light: Press frequency 60-80 beats/min
  Green light: Press frequency 80-100 beats/min
  1)right operation: 2 green lights on Press frequency >100 beats/min
  2)red light flashing:compression depth insufficient