traxxas 2.4GHz radio

[kulangflow]

I'm pretty sure it is an independent 4th channel, but we just can't see the toggle in the previous picture because it's hidden by the steering knob.

This next picture shows the 2 channel version, but if you look at the rx, you'll see it has 5 total inputs including 2 x Ch1 for the dual servo use and separate channels for 2, 3, and 4.