Abstract: An instruction or identification card or badge for use in a time recording system, to authorize admission to restricted locations or for use in credit transactions comprises layers of material that is opaque to visible light but transparent to infra-red radiation. A code that is readable by an optoelectronic reader but is invisible in ordinary light is provided by transparent windows alternating with infra-red opaque regions arranged along a line parallel to one edge of the card, one binary digit being represented by wide rectangular windows and the other binary digit being represented by narrower windows that when read in a badge reader give different peak heights. The code is self-clocking and need occupy only a small portion of the card area.

Abstract: A data recorder for use in processing cards and the like comprises a housing which has mounted therein electronic control system incorporating both firmware and software programs. A thermal printer and optical reading device are mounted in the housing for printing information onto the card and reading information on the card respectively. The data recorder may be used as a clocking-on device and special cards provided for changing at least one of the software programs of the electronic control system.