Name QuorTech (formerly Elcotel) COCOT Phones
Maker QuorTech (formerly Elcotel) 
QuorTech/Elcotel is one of the leading makers of COCOT phones in the USA. The Western Electric Fortress (originally made by WECO/Bell/AT&T) is now known  Olympian 5501. It is now owned, manufactured, and refurbished by QuorTech Solutions. Offering user and operator familiarity, the Western Electric style payphone is the industry standard and is the most widely utilized payphone in the USA.

Elcotel was a manufacturer of pay telephones. They were recently purchased by QuorTech. The QuorTech web site has been updated to mention the Elcotel product line. The most common Elcotel model in use is the Series 5. There is also the Olympian 5500, for use in Western Electric housings. There are also some discontinued models, such as the Gemini III, but those are rarely used anymore. A recording of a discontinued model is available below.* Elcotel also has some new, advanced models, such as the Komet, which AT&T local services likes to use, and the Eclipse, which is used mostly in Canada. These new models have LCD displays and card slots, and use 2400 baud modems, which are faster than the 1200 baud modems used by the Series 5 and Olympian models. All Elcotel phones behave in the same way, and have similar sounding phone voices. Elcotel phones are line powered, and will not do anything if you leave them off hook too long. During the time you dial a call on this phone, the phone will slowly redial your number, and you can hear it faintly in the background. It will even do this while waiting for you to pay. These phones take your money at the end of a call, and if you don't deposit enough money it will say "Please deposit an additional whatever." They have human sounding phone voices that sound like this. When you call them, you can have a lot of fun with them because you can dial numbers with your touch tone phone and the phone will think you are dialing out from it. You have to wait until the modem stops to do this though. I have recorded an example of dialing after the modem. I have also recorded a call where I don't do anything. At the end of the call the phone just says its number and how much money it has. Some Elcotel phones are set up so that they will not say their phone number or how much money they have at the end. I have also made a recording of the ringer from most modern Elcotel phones available.
Ringer from newer Elcotel models
Call and do nothing
Call and dial numbers
Recording of a discontinued Elcotel model  
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 payphones, 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