Thank you for your explanation.At first glance I thought the input and output ends of the DC/DC converter were reversed. Might be a good idea to mark them on the diagram for someone like me :).

Looking forward for your alternative builds, maybe I'll be tempted to give my old bleeper the shock of its life. 

Keep it up!

::THUMBS UP:: You definitely should, I will also see I can figure out the pinouts for some other pagers I have if I can find them, as the software is not Motorola Advisor specific, the project should work with any POCSAG or GSC pager.

Check out the videos of it in action, integrating my pagers with asterisk is a real throw back.

According to your schematic the ESP is being supplied with 1.5v on its 5v in pin

It is being supplied with 3.7v, if you look, the pagers battery was replaced with a 10440 and goes into an 18650 bms to provide low voltage discharge protection, and the 3.7v is within spec of the VIN of the ESP32 albeit on the low end, remember it is 4.2v when fully charged.

The better choice than the supermini would be the XIAO ESP32 C3 as it provides battery input pins and can charge the battery.  Standby in the next couple days I will show alternative builds.  I have a build that I cut the case to expose the usb c connector of a XAIO ESP32C3.