RE: the unofficial home of the dumas dauntless
Here's a quick history of the radiophone for folks like me who aren't familiar with them --
After the second world war, a few radio telephones were fitted into the automobiles and yachts of the rich and important.
These units worked by connecting to one or more base stations, and were half-duplex (meaning that although the transmit and receive frequencies were different, you could either talk or listen, not both at once).
The transmitters had output powers of 20 or more watts, and the areas they worked in were restricted to the range of their signal.
Because of the wide channel spacing and high powers used, combined with the limited range of frequencies available, there was only capacity for a few thousand radio telephones across the country.
As with early fixed phones, calls had to be connected by an operator, and it was some years before automatic exchanges were widely introduced. There was no possibility of hand-portable units: these devices could run a car or boat's battery down quickly if you weren't careful!