This invention is in the field of bar code scanners.  More specifically, the invention relates to point of sale bar code scanners, and the problem of efficiently validating redemption coupons used at retail stores.  More broadly, the invention is concerned with the redemption of anything of value bearing a bar code in a retail purchase transaction, including food stamps or other redeemable certificates. 
Point of sale (POS) bar code scanners are in wide use in retail situations such as grocery stores, drug stores and general merchandising stores.  Many of the stores which utilize or could utilize POS bar code scanners for scanning products for purchase also routinely honor coupons which grant the bearing customer a specified rebate on the purchase price of specifically identified items, usually within a prescribed period of time, prior to an expiration date.  Each coupon usually specifies the item, its size, the value of the coupon against purchase of the item, and the expiration date.  A customer may receive these coupons in several ways, such as from newspapers or magazines, from direct mail advertising, from purchase of another product, or of the same product at an earlier date, or from coupon books. 
In typical use, these redemption coupons have been returned to the manufacturer or distributor of the affected products, for validation and reimbursement to the retail store by the manufacturer or distributor.  The manufacturers or distributors have required this as a condition of reimbursement to the retailer. 
However, this practice has been cumbersome and time consuming for the retailers and also for the manufacturers.  Further, there was no guarantee to the manufacturer or distributor that the coupon was actually used within the allowed time period since there was a lag in time between redemption to the customer and return of the coupon to the manufacturer.  The manufacturer did not even have sufficient control to assure that the proper purchase occurred for acceptance of the coupon. 
Recently, there has been a move among manufacturers, coupon distributors and retailers toward a system in which return of the redeemed coupons to the manufacturer or distributor would not be necessary.  A Joint Industry Task Force of food retailers and grocery manufacturers has been working on a uniform type of system for this purpose.  The Task Force has been charged with setting standards and expediting the installation of coupon scanning and electronic clearing.  It has been determined that bar codes will be put on redemption coupons.  In such a system, strict validation and securing procedures would have to be followed at the point of sale, and with an appropriate reporting procedure to the manufacture so that validated, genuine transactions could be accurately reported and reimbursed to the retailer, eliminating or reducing the discretion of the check-out person. 
One ultimate aim of such automated coupon processing can be electronic clearing of redemption coupons, similar to electronic banking, wherein the manufacturer is debited and the retailer credited automatically, eliminating several levels of manual clearing. 
In contemplation of such a retail point coupon validation system, Advanced Promotion Technologies has marketed a system under the name Vision 500 Coupon Eater which consists of a redemption coupon reader and invalidator.  Invalidation can comprise shredding or inking.  This piece of equipment was designed to be used in connection with a point of sale retail bar code scanner, with information from the POS scanner sent to the coupon reader/shredder as to the content of the consumer items presented for purchase.  The auxiliary coupon reader and shredder could then validate the actual purchase of each item as specified in the coupons presented for redemption, and validation could be made electronically in this way, with credit issued to the customer for redeemed coupons. 
While the described auxiliary coupon reader system would appear to address the problem of efficient coupon validation, it required an additional piece of equipment and a cable interconnection with a product bar code scanner.  It was connected generally between the scanner and the POS system (the terminal or cash register), and as such potentially could degrade product bar code reading performance.  In this sense, the described previous system was inefficient and costly as compared to the present invention described below. 
Another device aimed at validation of coupons is disclosed in U.S. Pat.  No.  4,839,507.  However, the system of that patent involved a separate machine for dispensing coins in redemption of coupons and it involved insertion of two coupons simultaneously.