A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 1990 / A debit-card is a form of payment, The card is pre-charged with a value, monetary or otherwise, before distribution to the user, and is therefore a pre-payment card . It is then 'used up, its value being decremented until it is valueless. At this point, it is either discarded or re-charged by the administration authority, It is distinct from a credit card, which provides a post-payment facility. The aim of this project is to investigate the security aspects of a debit-card reader system for use as an unattended fee-collecting subsystem in such applications as public telephones, parking meters and vending machines. Card technology and attributes of debit card systems are discussed, an overview of cryptology is given, and an implementation of a magnetic card system is described.