A portable credit card reader is a widely used device today, as the days of 'cash' money are passe. Everywhere, plastic money is replacing cash. By plastic money, I mean debit cards and credit cards. Consequently, portable credit card or debit card readers are required in almost all commercial retail establishments and shops now. A credit card is absolutely useless if there aren't credit card readers! So the credit card companies themselves, encourage and bring about tie-ups and deals for manufacture and distribution of card readers. The aim of this Buzzle article is to demystify the working of a portable card reader. Working of Portable Credit Card Readers Portable magnetic card reader technology is based on the use of microcontrollers. Before we try to understand how a portable credit card reader works, let's understand how a magnetic card is encoded with required information, which is then read by the card reader. Credit cards have a magnetically encrypted code written in them. This code is encoded on the card, in three magnetic strips, that vary in their bit density. This code is encrypted in such a way, that none other than the card reader can read it, as it's exclusively supplied with the decryption key. The procedure for production of these magnetic cards is standardized now and all of them are produced by a similar process. The three magnetic strips hold 79, 40 and 107 characters respectively. Data is written in these strips by using a technology called 'Two Frequency Coherent Phase Recording'. The data to be written varies, according to the utility of the magnetic card. A magnetic card can be anything, from a credit card to an official RFID card. The first track of a magnetic card contains alphanumeric data, while the rest of the two tracks are strictly encoded with numbers. There are certain bits in the strip code that tell the card reader from where to start reading or stop reading. They are called 'sentinel' bits. As mentioned before, a portable card reader is a microcontroller device with embedded software and hardware designed to read the magnetic strips on the cards. It has a read head, one for every track that reads the encrypted code. To get the card read, it needs to be swiped through the reader. Every microcontroller in the card, requires clock cycle input for operation. It's also provided with the requisite oscillators that can provide the same. It reads the encrypted code and decrypts it into original data with the help of the microcontroller program. The reader is programmed to identify and authenticate a card. Every credit card company supplies its own authentication credentials and microcontroller program to manufacturers. The credit card companies and the portable card reader manufacturers have a legal agreement, so that sensitive customer data and information is not disclosed. The portable credit card is of course provided with an alphanumeric keypad to enter the details of transaction before and after the card is swiped and read. What makes a portable credit card reader portable? The reader is provided with a wireless connection with the bank server or to the local computer of the respective shop or the super store. That local computer is then connected to the bank server. The reader needs to have an updated database of information, regarding the customers details of that credit card company or bank. This information is updated from the bank server, through the wireless connection. Thus credit card readers provides a complete solution for credit based shopping. Thanks to them, one has no need to carry cash everywhere.