How to simulate classic old dial tone sound with a Grandstream ATA

[Bay Area Doug]

I thought it would be a fun addition to my home collection to have the rotary phones sound as vintage as possible. The old dial tone sound that was used in the US during the direct dial transition can be simulated. It sounded like this at the time:

https://youtu.be/uaQm30DDHL8

From what I have read, it was a 600hz tone modulated at 120hz.  Your Grandstream HT502 or HT802 (likely others) can simulate the sound.  In the Advanced Settings, Dial Tone:, you will see this:
f1=350@-17,f2=440@-17,c=0/0;

Instead, Use this syntax:
f1=600@-17,c=4/4;

The operators synthesize a 600hz tone, at -17dB, cycling on and off at 4 milliseconds. I found this combination works best, and although it is probably more square-wave sounding than the original (the modulation is square not sine), it's not bad at all.

The potential for expanded personal joy is important to appreciate here.  In the past when I challenged some kid to make a call, he starts out bewildered, pokes at the dial, maybe figures out how to turn it, inevitably needs to be shown the unit needs to be off hook or you can't dial, etc., intertwined with mocking laughter. Now add to that the shocked look on his face when confronted with an unfamiliar dial tone.  You get the picture.  Pure satisfaction on my side.