>Hi,
>
>such a system already exists, amateur radio; they also have protocols
>for sending short text messages; and they have an independent
>non-commercial infrastructure that is global

Yes Armin, but amateur radio needs a lot of electric energy, licence
for emitting, there is no freedom of conversation, no point to point
communication, no mesh networking, the materials are very heavy, the
materials are expensive, and requires a lot of knowledge= all exactly
the opposite of the bricophone concepts explained since 2007.

oh, yes, hacked-SDR radio hardware on RasPi or similar nanocomputer
are relatively low cost, low consumption and lightweight but they
need too much knowledge and additional environnement to be considered
as "phones", they still don't reach one person at a time, and they
are impossible to find where bricophone are needed.

JN