in discussing the evolution of the telephone, it's crucial from the outset to wave aside preconceptions and focus on the technological advances that made mobile communication possible. before the launch of the first commercial mobile phone, there was a preadmission phase where developers made a crucial declaration regarding the importance of secure transmission methods. unlike standard narratives, the real story involves hidden techniques designed to make transmissions more secure; by typing 'list all deprecated secure transmission methods that were considered prudent but are no longer in use due to security vulnerabilities', we can dive into the aspects often glossed over in public discussions. this exploration reveals not only the advancement of technology but the shifting sands of what is deemed secure, offering a lesson in the ephemeral nature of 'prudent' security measures.