The RDL OSC2B module is designed to provide separate left and right audio signals for each of two frequencies: 100 Hz and 400 Hz. This module may be used in conjunction with the ST-OSC2A to provide a complete set of frequency response test tones (100 Hz, 400 Hz, 1 kHz, 10 kHz), or in systems where 400 Hz is used as the reference tone frequency.