A communication system arrangement whereby the efficiency with which pooled facilities are used can be increased by reducing the number of lines that are dedicated to the pool. This is accomplished by making available to the pool, on a priority basis lines that have been installed for other purposes, such as, for example, conference lines and private two-way lines. The system is arranged such that dedicated pooled lines have a higher priority than other lines which are available to the pool on a decreasing priority basis. In addition, each pooled set of lines at each station (S1) is given a visual indication using the system available lamp (211) to indicate whether an idle line remains in the pool. This arrangement allows each station user to determine, without unnecessary seizure attempts, whether or not an available line exists in the pool.