I have an interest in telephony, and to further it, I recently bought
> a COCOT for personal use to play around with.
> Another interesting behavior I've noticed is that while you're dialing
> a number, but before you deposit any money, it beeps out the DTMF for
> the number to be dialed extremely slowly over the line. If you don't
> deposit any money by the time the number is about to be completely
> dialed, it will hang up. After you deposit the money, it will pick up
> again and dial the number quickly. Does anyone have any explanations
> for why it would do this? The circuit board inside is described as an
> "Elcotel Series 5," if anyone is curious.
This is called trickle dialing. The phone relies on the line for power, so it's gone off hook to get voltage while it's interacting with you. The digits are being dialed in order to keep the dialtone from timing out. This also keeps the phone from ringing in while you are off hook.
Despite all the oddities, having your own pay phone sure is fun.
Did you get software, so you can reprogram it to do what you want it to do?