Sidetone is extremely valuable to confirm the intercom is operational and help the speaking rider modulate their volume - the Autocom I'm hoping to replace with the 20S does it beautifully.
The 20S V1.6 has just enough delay between the speaking rider and the audio to the speaking rider to create noticeable, and annoying, echo. From my own job experience developing audio communication systems I know a human can detect delays as low as 6ms and would find a delay approaching 20ms as unusable. I've disabled sidetone, for now, but would appreciate Sena improving (reducing) the delay between the speaking rider and the audio heard by the speaking rider to no more than 4ms. Some path optimization in the FW should be able to do this.