A voicepipe system at Friar's Keep which is effectively an Arcadian intercom. A large funnel carries the speaker's voice down a series of metal tubes and is carried to the listener at the other end. At Friar's Keep the largest 'in' tube is outside the main door, with Warden Murron minding the other end. There is probably also a network of tubes internally as well, so the guards such as Dagdam Yiru can communicate with Murron and the other floors.
Although reminiscent of the pipes Burns Flipper used to screen visitors to his warehouse in TLJ, in the real world speaking tubes were mainly used aboard maritime vessels. It is possible that this is Azadi technology employed aboard their Cloudships and installed in Friar's Keep for security purposes, although it must be remembered that the Keep stood before Azadi occupation.
The only other analogous system in Arcadia is the network of Dolmari Telephone Statues on the island of Alais, but those statues appear to be purely magical rather than the magic-technology mix characteristic of Azadi machines.