Telepen is a British barcode that can hold every ASCII character. It's used mostly in the United Kingdom, by libraries, universities and the motor industry.

What it holds
Characters	Standard: letters in both cases, digits and the symbols of plain ASCII, the ones on a US keyboard - no accented letters, and no £ or €. Numeric: digits only.
Length	Up to 30 characters in Standard, 60 digits in Numeric.
Check digit	Always there: a check character worked out by Labeljoy. It isn't in the readable text.
Modes	Standard or Numeric, which packs digits two to a character and so holds twice as many. A scanner reads one or the other: choose the mode yours is set to.
Readable text	The value, under or over the bars. In Numeric, an odd number of digits gets a 0 in front.

Numeric with an X. In Numeric the second digit of a pair can be an X, as in some library numbers: 123X is allowed, 12X3 isn't.

Characters you can't type. In Standard, a tilde followed by three digits is the character with that code - ~009 is a tab - and ~~ is a tilde.

The rest of the settings - text position, quiet zone, color - are in the Barcode section.

What goes wrong
Invalid characters in input data.	The value has a character the mode can't hold: an accented letter, or anything but digits and X in Numeric.
Invalid position of X in Telepen data.	In Numeric, an X that isn't the second digit of a pair.
Input data too long.	More characters than the mode holds.