Coin Telephone NT 2000: Modern Technologies Clear the Way to Global IDDD

The paper describes the concept and subsequently the design of the new Coin Telephone NT 2000 which is suitable for global international direct distance dialing. 1) The NT 2000 can be connected to the switching system like a normal subscriber station, i.e., without additional equipment being required. 2) It can handle several coin denominations; a digital display continuously informs the user of the credit balance. 3) An indirect collection method ensures optimum utilization of the money deposited; remaining credit can be used for an additional call. 4) The telephone is very simple to operate thanks to ergonomic design and easy-to-understand pictogram instructions. The design of the NT 2000 demonstrates the application of stateof-state-of-the-art technologies. 1) Almost the entire information processing section consists of customized MOS circuits. 2) Inserted coins are not tested and sorted mechanically but "electronically." 3) The few mechanical devices still left are very simple to handle. 4) The telephone is modular and, therefore, very simple to maintain and operate. Thanks to its universal design, the NT 2000 can be used in many countries without major modifications.