Seems the picture is wrong. The Olympus homepage does show a USB connector:
https://www.olympus.de/site/de/a/audio_accessories/accessories_professional_dictation/hand_foot_controls/rs28h_footswitch/index.html
The foot control is only compatible with the following Olympus software:
DSS Player for MAC version 7 (or higher).
Olympus Sonority version 1.0.1 (or higher)
ODMS Version 6 (or higher)
DSS Player Pro Version R5.0.0 (or higher)
This will hardly work for Windows Media Player.