A communication installation for use in a site having underground galleries, for information exchanges, comprises a repeater connected to a wired distribution network. The repeater is arranged for receiving messages which arrive over the wired network at a first frequency and for retransmitting the messages over the network at a second frequency different from the first frequency. The network comprises non-radiating cable sections, radiating cable sections capable to radiate at the second frequency and to collect radiation energy at the first frequency from a portable emitter-receiver set placed nearby. The network further comprises terminal antennae for emitting at the second frequency and collecting energy at the first frequency.