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There are three tracks on the magstripe. Each track is .110-inch wide. The ISO/IEC standard 7811, which is used by banks, specifies: * Track one is 210 bits per inch (bpi), and holds 79 six-bit plus parity bit read-only characters. * Track two is 75 bpi, and holds 40 four-bit plus parity bit characters. * Track three is 210 bpi, and holds 107 four-bit plus parity bit characters. Your credit card typically uses only tracks one and two. Track three is a read/write track (that includes an encrypted PIN, country code, currency units, amount authorized), but its usage is not standardized among banks.The information on track one is contained in two formats -- A, which is reserved for proprietary use of the card issuer, and B, which includes the following:Start sentinel -- 1 characterFormat code="B" -- 1 character (alpha only)Primary account number -- up to 19 charactersSeparator -- 1 characterCountry code -- 3 charactersName -- 2-26 charactersSeparator -- 1 characterExpiration date or separator -- 4 characters or 1 characterDiscretionary data -- enough characters to fill out maximum record length (79 characters total)End sentinel -- 1 characterLongitudinal Redundancy Check (LRC), a form of computed check character -- 1 character The format for track two, developed by the banking industry, is as follows:Start sentinel -- 1 characterPrimary account number - up to 19 charactersSeparator -- 1 characterCountry code -- 3 charactersExpiration date or separator -- 4 characters or 1 characterDiscretionary data -- enough characters to fill out maximum record length (40 characters total)LRC -- 1 character
What are they? 10x1cm!So how much data could they hold?
Could a magnetic strip hold a few seconds of video and audio when swiped over a revolving video cassette head ?
The standard for magstripe cards involves an eighth-inch wide track, and a low recording density. A standard VHS video track (let's keep it simple, forget about digital wizardry) is only 19um wide, and uses a helical scan with a stripe just under 4" long (about the same as a credit card stripe)... therefore in principle you could record about 668 video fields on a similarly-sized piece of videotape, equivalent to just over ten seconds of recording.Edit: this doesn't "feel" right - especially not with a roughly 1-inch per second linear tape speed. Where have I gone wrong?
Ignoring the fact that the tape on the back of a credit card was never designed to hold 19μm wide tracks, and would certainly have enormous crosstalk problems if you tried, I am still not sure where you get the 668 video fields from (but then, I don't say I know enough about video encoding know what the numbers should be).