I have now also put together a first prototype of the even more functional, modular Retrophone. The basic functionality is comparable to the normal Retrophone, but expansion cards can be used to create a custom Retrophone that can ring the connected telephone, speak the time, read sensors and switch external (230 volt) devices.
Due to its modular construction, this Retrophone can be tailor-made for stage performances, film recordings, museums, exhibitions and escape rooms, etc.
The experiments have been done, the print designs have been made and even a first prototype with a full diagnostic pcb, with which all signals can be monitored, has now been assembled. For the time being, the priority is first to document and further complete the basic Retrophone. For this reason, this page and the video are currently still under development, so come back here soon for the sequel!