The SITA network is one of the oldest networks in the world, predating networks like Arpanet which would be know as 'The Internet'.

SITA started off with a telex network which quite soon was equipped with so-called HLS systems (High Level System). This is a very early diagram of that network (click on the picture for a large version):

Once this network was no longer sufficient there was a new network put in place which incorporated the above shown network but which also brought in many new components (click on the picture for a large version):

After this network become obsolete it was incorporated in an even larger (and boring...) TCP/IP network.