Volumes I and II of the Signals series were combined into one volume. This two volume reprint looks at the organisation of 26 Group, 60 Group and the Signals Branch at the Air Ministry. One of the elements of C3I is "communication" and the speed of air operations and the need to get information from and to commands was (and is) fundamental to all operational command and control. The first volume deals with just that. The second volume deals with the telecommunications systems developed for RAF use throughout the war. Telecommunications were important for security reasons,: they were much less susceptible to interception (and remember that the Germans sent their most secret messages via teleprinter whenever possible). Although seemingly very ordinary, the story of these systems is all part of the electronic warfare of World War Two.