Verifying Google Voice

I've been struggling getting my work phone number verified with Google Voice. The way that number verification works is that Google Voice calls you and asks you to enter the two-digit code that's displayed on the website. But for some reason when I get a call on my outside line and I press a number button, it doesn't send that DTMF tone. Instead it tries to place another call.

My solution? I found a DTMF tone generator online and I played the code DTMF tones through my computer speakers.

It's nice to see that these old phone tricks still work.