HP-42s double speed modification and printing

[Diego Diaz]

Hi Bernd,

The IR signal is in fact a modulated series of pulses. A carrier is switched ON/OFF according to the transmitted data.

The receiver detects (and then filters out) that carrier, extracting the data pulses and passing them to the printer mechanism.

Since the carrier frequency depends on the HP-42S clock it can no loger be detected at 2x and hence the printer won't work at all.

That's why all my 2x mods to 42S inlcude a switch to revert it temporarily to the original speed when printing.

Hope you find this info useful.

Best wishes.

Diego.