units

Millennium
Nortel originally developed the Millennium pay phone, but recently, that product division was sold to QuorTech. It has a digital display and it has a card slot as well as a coin slot. Some models have card slots only and take no coins. There is also a desktop Millennium model, which has the same display as the pay phone style model, but looks more or less like a Nortel Meridian business phone. For some odd reason, Millennium pay phones do not have a coin return lever. The Millennium phone also has a second language option which changes the phone voice and and instruction readout. In the USA the second language is usually Spanish, while in Canada it's French. You can listen to the Millennium's phone voice in all its available languages, which are English, Spanish, French, and Japanese. These phones operate on a normal phone line with the extra polarity reversal option. Polarity reversal is used to signal the phone that a call has been completed. When the call completion is detected, the pay phone will take your coins immediately, if you made the call using coins. It produces a fake dial tone, and has instructional voice prompts. If you do not pay enough money for your call, it tells you how much you have already paid, and how much you have left to pay. If you leave it off the hook for too long, it tells you to hang up and then start again. Because this phone has lots of advanced features, it requires an AC power source to operate fully. If the phone is unplugged from its power source, you can pick it up and get a real dial tone, but the keypad will only work if you dial phone numbers that phone is programmed to let you dial for free. Millennium phones, when they are connected to lines which allow incoming calls, have fairly loud ringers. A recording of the ringer is available for your listening pleasure. Lately, many Millennium phones have been programmed to dial # when an incoming call in answered as an anti-fraud measure.

COCOTS
A COCOT is a Customer Owned Coin Operated Telephone. It is a pay phone which is not owned or operated by the local phone company. Unlike phone company pay phones, COCOTS do not usually run on a coin line, they just run on a normal phone line. For a brief period some COCOT companies have were using ordinary fortress phones on coin lines, but they're not around anymore. COCOT phones have computer-like circuitry in them and they handle all the billing for the calls placed on them. COCOT phone companies have always used this type of equipment, but lately, some local phone companies have started using COCOT equipment in their pay phone service.  

with thanks to  http://www.payphone-directory.org/phones.html

special thanks to www.dmine.com