The Millennium line was introduced in the mid 1990s and allowed the use of coins (5, 10, 25 cents and 1 dollar for Canadian versions) and cards (credit card or phone cards as well as “smart” chip cards.) They were equipped with an advanced electronic coin validator, which could detect slugs or coin blockages. The phones themselves are quite complex, using a Zilog Z180 processor with a number of peripherals attached. The whole point of the Millennium system was security and advanced monitoring. All Millennium phones connect to a server platform called Millennium Manager, which allows the operating company to control and monitor virtually every aspect of a phone. The phones 'call home' on a regular basis, uploading CDR records if they are full and reporting coinbox status (down to the amount of coins in a given denomination). The coin vault lock has a small micro switch that can detect break ins, which will cause the phone to call into the Millennium Manager with an alarm. The main housing lock also has a similar switch, which if triggered without entering the craft interface beforehand will trigger an alarm as well. Millennium, with its Vacuum Fluorescent (VFD) display, is certainly one of the most iconic payphones ever made. More on Nortel Payphones on wikipedia.
Millennium payphone must be configured to connect to the NCC (Network Control Center, aka. Millennium Manager) before it can function. The payphone accesses the NCC via a built in modem. The connection is made using Bell 212A standard at 1200 baud, 8 data bits, 1 start bit and no parity.
Another way to use the payphone at home is to install a custom demo firmware (but it works with older control board only).
Different hardware revisions existed with multiple firmware versions, even though they look similar from outside. The most common multi-pay stations had two major revisions of the control board: thru-hole process (below: left) and SMD, which allows electronic updating of firmware.