[extraduder_ire]

Is there a spec for these anywhere? the , and ; specifically.

This sounds like it exactly solves a problem I have in automating interaction with my phone carrier's IVR interface for adding billing credit. Each of the delays are different, but predictable, and the whole process is about 30 seconds long.

[shakna]

DTMF [0] which also points to SDP, along with the tel scheme RFC [2]. It's a bit of a rabbithole to find what exactly is supported.

[0] https://www.rfc-editor.org/rfc/rfc4733#section-2.4.1

[1] https://www.rfc-editor.org/rfc/rfc3555#section-3

[2] https://www.rfc-editor.org/rfc/rfc3966#section-5.1.3