=Introduction= A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user.
=Challenges=
=Approaches= * [https://www.crowdsupply.com/arsenijs/zerophone ZeroPhone] * [https://www.pine64.org/pinephone/ PinePhone] ** [https://github.com/dreemurrs-embedded/Jumpdrive Jumpdrive] * [https://librecellular.org/ Libre Cellular] * [https://hackaday.io/project/170878-armachat-doomsday-wireless-qwerty-communicator Armachat]
=References= * [https://en.wikipedia.org/wiki/Telephone Wikipedia: Telephone] * [https://ubuntu.com/blog/introduction-to-open-source-private-lte-and-5g-networks Ubuntu: Introduction to open source private LTE and 5G networks] * [https://en.wikipedia.org/wiki/OpenLTE Wikipedia: OpenLTE] * [http://openlte.sourceforge.net/ OpenLTE] * [https://sourceforge.net/p/openlte/wiki/Installing%20OpenLTE/ Sourceforge: Installing OpenLTE] * [https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.695.1244&rep=rep1&type=pdf FPGA Implementation of LTE Downlink Transceiver with Synchronization and Equalization] * [https://www.eetimes.com/implementing-lte-on-fpgas/# Implementing LTE on FPGAs] * [https://www.gnuradio.org/about/ GNU Radio] * [https://en.wikipedia.org/wiki/Software-defined_radio Wikipedia: Software defined radio] * [https://telecominfraproject.com/openran/ OpenRAN] * [https://en.wikipedia.org/wiki/Radio_access_network Wikipedia: Radio Access Network] * [https://www.openbts.org/ OpenBTS] * [https://www.osmocom.org/ OsmocomBB] * [https://postmarketos.org/ PostmarketOS] - real Linux OS for phones