Clay tablets send messages in time and are more reliable in that way. The message is broadcast continously on a short distance (as far as reading distance), it

Clay tablets send messages in time and are more reliable in that way. The message is broadcast continously on a short distance (as far as reading distance), it does not require any form of energy and if no other circumstances are completely destroying the artefact (it could still be pieced back together if broken) it could last a really long time, well beyond any modern technology