Digital phone and Mobile phone

Mobile phone and digital phone are semantically related In some cases you can replace phrase "Mobile phone" with "Digital phone", this phrases are similar.

Mobile phone noun - A hand-held mobile radiotelephone for use in an area divided into small sections, each with its own short-range transmitter/receiver.

Digital phone and mobile phone are semantically related in cellular telephone topic. You can use "Digital phone" instead a noun phrase "Mobile phone".