Improvements relating to automatic inventory systems

876,170. Indicating availability of seats. ELECTRIC & MUSICAL INDUSTRIES Ltd. Nov. 29, 1957 [Nov. 29, 1956], No. 36484/56. Class 106 (3). An automatic inventory system comprises a plurality of subsidiary stations each including an availability record and means for testing availability by reference to said record in response to a reservation enquiry signal, and a main station comprising means common to the subsidiary stations for deriving availability record-correcting signals in response to reservation signals from the subsidiary stations, means for transmitting said correcting signals to each subsidiary station at intervals and means at each subsidiary station for updating the respective availability record in response to the correcting signal. The system may employ a teletype channel and may include a plurality of hand sets, connected to the subsidiary stations by the teletype channel. Fig. 1 shows diagrammatically the general layout of an inventory system used by an airline. An enquiry about availability of space made at a subsidiary station or at a sales office connected to the subsidiary station, starts a cycle of operations as follows: by operating the hand set, the agent, connected to 1, obtains a availability reference from 2. If favourable, the reservation is recorded at 2 and re-checked by 4 according to information received from other substations. Cancellation signals are recorded in the same way. At predetermined intervals aggregated reservations and cancellations recorded at subsidiary stations are sent to the main station and recorded by a computer which comprises a space-control inventory 6. When the space control inventoty has manipulated incoming signals, amendment information is compiled and transmitted by means 7 to the subsidiary stations. If, in response to an enquiry the availability testing means 2 indicates that no seats are available on a particular flight, the inventory system has facilities for transferring particulars to a wait-list control apparatus 8 located at the main station. This wait-list control apparatus is arranged for the transmission of signals via 9 to the appropriate reservation offices for contacting passengers if seats become available due to cancellations or other reasons. The apparatus at the subsidiary station or sales office connected with it, may include means 10 for storing passenger records for ultimate transmission to the departure points of the respective flights, so that passengers can be checked into a