This was a quick project made as a gift for Christmas. It uses the Element14 Schematics as a base, but expands upon them for updated components and features.
Despite being a short project, it was a great learning experience, to learn more about analog systems. This was a purely hardware solution, which was really interesting to develop, as it required no code.
Features:
- 6 Phone Intercom lines
- Additional expansion supported (up to 9 lines)
- Single Button dialing
Skills Learned:
- PCB Design (KiCAD)
- DC/AC Converter
- Current Sources
- Plain Old Telephone Service (POTS)
- Demux Chips
- DTMF Receiver and Decoding
- Relay Control
Inspirations:
Hardware:
- 18V Transformer
- MT8870DSR1 (DTMF Decoder Chip)
- CD4514BM (Demux Chip)
- LM317T (Used as a current source)
Versions:
Rev 1 - No official revision, as I only made one
Instructions:
No instructions exist for this project. It was designed as a one-off. I would suggest looking at the Element14 post linked above, and adjusting it for your needs. While the post above is outdated now, the principles and basic application are still relevant.
Can I buy this?
No, I built this for myself, and hence is not something I'd consider reliable. I have no interest in selling one.
Images:
In person photos to be added later
