The Nokia DCT4 platform is famous for housing some of the best-selling mobile phones in history. The Nokia 1100, a DCT4 device, has sold over 250 million units, making it the world's best-selling phone. Its simple, durable design captured the global market. Other popular DCT4 phones include the Nokia 3510i, 3650, 6600, and the N-Gage. Understanding the platform is key to appreciating the "calculator" tools designed for it.

: Designed to unlock the specific network lock.

The Mobile Country Code and Mobile Network Code of the original carrier the phone is locked to.

Perhaps the most famous of all. Rolis’s software was a standalone Windows executable. You entered the IMEI, selected the network provider (or entered the MCC/MNC manually), and clicked "Calculate." It supported DCT3, DCT4, and later BB5 phones. The interface was utilitarian, but it worked with near-perfect accuracy.

: A critical UI feature should warn users that DCT4 phones usually only allow 5 attempts