Making a century's worth of telephones useful again

The gCore POTS (Plain Old Telephone Service) shield contains the circuitry necessary to implement a local area "line card" - or Foreign Exchange Service (FXS) - providing the proper signaling for traditional 2-wire telephones. It provides all the functions necessary to make your old school telephone functional again. It has the following features and capabilities.

• Generates -48VDC line bias
• Generates ringing voltages
• Detects off-hook and on-hook conditions
• Supports rotary and DTMF dialing
• Supports audio via a 16-bit audio I2S codec
• Supports Caller ID generation

You can plug a telephone directly into its RJ11 jack or you can connect it to the existing wiring that might exist in your home or business and then plug one more more phones into other jacks around the home or business.

(Back when talking on the phone was glamorous)

Part of the weeBell project

I think old telephones are cool and the history of telephone development is quite interesting. I like the idea of making them useful again.

The gCore POTS shield was designed as an expansion board for gCore as part of my weeBell project. weeBell consists of a gCore POTs shield connected to gCore and a battery in a 3D printed enclosure. My goal with weeBell is to create a programmable platform that makes POTS telephones work in a variety of applications such as

• Bluetooth handsfree allowing calls to be made and answered using a cellphone.
• SIP support to allow VOIP telephony using a platform such as asterisk.
• Installation or prop controller letting a telephone be used as part of an exhibit or in an escape room.
• Whatever someone can think of (my source code is available to help out).

The gCore POTS shield is fully documented and can be used with your own controller and software if you like as well.

Software Support

Currently the open-source weeBell_bluetooth ESP32 IDF project uses the classic Bluetooth Handsfree profile to let phones attached to weeBell make and receive phone calls with a paired cellphone. Support for ring patterns and dial tones for a growing number of countries. You can even dial 0 to call a virtual operator (Siri on iPhone or "Hey Google" on Android).

My goal is to work on a SIP version that will use Wifi to communicate with a server such as an asterisk instance to allow VOIP telephony. And I'd also like to create a version of code that lets people call phone numbers and hear various pre-recorded messages played back from a Micro-SD card inserted into to gCore, and perhaps even leave messages at various simulated voice mailboxes.

All my weeBell code will be available for easy download using gCore's Serial Programmer desktop application that gets the latest copies of compiled firmware from my website and runs on Linux, Mac or Windows platforms. Of course the source can be found on github.

Perfect for a gift

weeBell_bluetooth, in a 3D printed enclosure using my design or an even better enclosure you design, is a perfect gift for that person in your life who likes retro tech, wants to amuse others when they use the phone or simply prefers the feeling of talking into a solid telephone handset over a slab.

Buy kits and save

Buying a gCore along with the gCore POTS shield gets you the latest version of weeBell_bluetooth pre-loaded on gCore, a necessary expansion header pre-soldered to gCore and a kit of screws and stand-offs for installation in the 3D printed enclosure. STL files for the enclosure can be found in the gCore POTS shield github repository (Documentation link below).

Battery Information

gCore uses a 2mm JST PH battery connector (Sparkfun/Adafruit polarity) for a single-cell 3.7V LiPo battery (~500-2500 mAh capacity - 1000-4400 mAh capacity when gCore is configured for 1A charging). The weeBell 3D printed enclosure is designed for a single 18650 battery. You can get a battery from Adafruit (or Digi-Key) or make your own with a raw cell and JST PH cable assembly.