A portable telephone having a cover to which a functional module such as an electronic calculator or a clock module is detachably mounted. The cover is rotatably mounted to a body of the portable telephone. Plural kinds of functional modules are replaceably mounted to the cover, thereby making the portable...http://www.google.es/patents/US5335273?utm_source=gb-gplus-sharePatente US5335273 - Portable telephone and multifunctional protective housing therefor
Portable telephone and multifunctional protective housing therefor
