"Dial Tones" on MWARA?

I've been noticing that there is some sort of DTMF tone on MWARA. It seems to come after the controller says "stand by for...". What is this for?

Ah. That's what it kind of seemed like. I just recently began listening to MWARA, after going through a half-dozen different HF antenna setups. It finally took a 8-foot tall stainless-steel antenna mounted on a 9-foot tower to do it.

That also explains what the rest of the "stand by for..." was. I was thinking it was "cell call", but I guess it's "stand by for SELCAL".