A fully automatic bar code symbol reading system having at least one automatic portable bar code symbol reading device, and an associated base unit positioned within the data transmission range thereof without a physical wiring connection thereto. After each successful reading of a bar code symbol,...http://www.google.se/patents/US5808285?utm_source=gb-gplus-sharePatent US5808285 - Portable code symbol reading device with one-way wireless data packet transmission link to base unit employing condition-dependent acoustical signalling for data packet reception acknowledgement 
