What Telepen is
Telepen is a standalone, full-ASCII-capable linear barcode historically used for library, inventory, and industrial labeling. bwip-js's encoder supports two modes: Telepen Alpha (the default, one codeword per raw byte value 0-127) and Telepen Numeric (a digit-pair mode selected with the numeric option).
Generate it now
Enter your text or data to see a live Telepen preview.
Valid input
In the default Alpha mode, every character must have an ordinal value from 0 to 127 ("Telepen Alpha characters must have ordinal values 0 to 127"). The input may be up to 500 characters ("The input data is too long" beyond that). bwip-js computes its own checksum (a sum of codeword indices, reduced modulo 127) and appends it automatically -- there is no option to supply your own.
Key options
Supported options include numeric (switch to Telepen Numeric digit-pair mode instead of the default Alpha mode), includetext, and height. bwip-js's own real default for numeric is false (Alpha mode).
Output and printing
Export SVG for vector-precise label artwork or PNG for a quick proof.
Common uses
Telepen historically appears on library circulation labels, inventory tags, and industrial asset labels where full-ASCII data (not just digits) needs a compact linear barcode.
Example
See the live preview above, seeded with a bwip-js-verified valid value.
Size guidance
Telepen's bar-width ratio is fixed by bwip-js's own encoding tables and is not independently configurable beyond the height option.
Troubleshooting
In numeric mode, the input must have an even number of characters ("Telepen Numeric must have an even length") and may only contain digits (or "X" in an even position, "Telepen Numeric may contain only digits, or X in even positions"); in Alpha mode, any character with an ordinal value above 127 is rejected.
Related formats
Related formats: Code 128 (a general-purpose full-ASCII alternative) and the separately-covered Telepen Numeric generator (this same encoder's own digit-pair variant, toggled with the numeric option above).
FAQ
Do I need to compute Telepen's check digit myself?
No -- bwip-js computes and appends Telepen's own checksum (a sum of codeword indices reduced modulo 127) automatically. There is no option to supply your own.