Bill validation

A currency detector or currency validator is a device that determines whether bills or coins are genuine or counterfeit. These devices are used in many automated machines found in retail kiosks, self checkout machines, gaming machines, transportation parking machines, automatic fare collection machines, and vending machines.

The process involves examining the currency that has been inserted, and by using various tests, determining if the currency is counterfeit. Since the parameters are different for each coin or bill, these detectors must be programmed for each item that they are to accept.

In operation, if the item is accepted it is retained by the machine and placed in a storage container for later collection. If the item is rejected, the machine returns the item. If a coin is rejected, it usually drops into a container for the customer to take back. If a bill is rejected, the machine pushes the bill out and the customer must remove it from the slot in which it was placed.

Banknote acceptors

Also known as bill validators or bill acceptors, paper currency detectors scan paper currency using optical and magnetic sensors. Upon validation, the bill validator will inform the vending machine controller (VMC) or other host device of a credit via a parallel or serial interface. Various interfaces exist for the host device, including a single-line pulse interface, a multi-line parallel interface, a multi-line binary interface, and serial interfaces such as ccTalk, SSP, and MDB. Wrinkled or creased bills can cause these machines to reject them.

There are currently only a handful of companies manufacturing this equipment. Crane Payment Solutions, MEI, and Japan Cash Machine (JCM) are three of the largest, each maintaining dominance in a particular market segment. Other notable companies producing this type of equipment include Coinco, International Currency Technologies (ICT), Alpha CMS (Cash Management Solutions), Astrosystems, Money Controls, Pyramid Technologies, Validation Technologies International (VTI), Innovative Technology Ltd (ITL), Global Payment Technologies (GPT) and Jofemar. Recent innovations include remote auditing and reporting by these devices as part of an Automated Cash Handling network for amusement, banking, retail, casino and other industries.

Coin detectors

The basic principle for coin detection is to test the physical properties of the coin against known characteristics of acceptable coins. The detector evaluates the coin based on its weight, size, and/or magnetism, and then sends an appropriate electrical signal via its output connection. The next step is generally performed by the bill-to-coins exchanger.

Today, sophisticated electronic coin acceptors are in use in some places that, in addition to validating weight and size, also scan the deposited coin using optics and match the image to a pre-defined list, or test the coin's "metallic signature" based on its alloy composition.

Normal coins pick up microscopic deposits from human fingers. When a coin acceptor is used long enough, thousands of coins rolling down a ramp will leave enough dirt to be visible. The acceptor requires periodic cleaning to prevent malfunctioning. Coin acceptors are modular, so a dirty acceptor can be replaced with a clean unit, preventing downtime. The old unit is then cleaned and refurbished.

Some new types of coin acceptors are able to recognize the coins through "training", so they will support any new types of coins or tokens when properly introduced.

See also


  • A Honeywell document about the different types of coin acceptors
  • Currency Detector Easy to Defeat
  • Cash automation research at Self-Service World
  • Astrosys International (Microcoin/GBA) Coin Validators and Bill Acceptors website
  • Crane Payment Solutions
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