PART III COMMUNICATIONS – SIGNALS CHAPTER XI SIGNALS Art.91 - Sound Signals : A - Normal manoeuvre: B - Obstruction in channel
![A WWII Air Ministry issued Aldis Signal lamp, 5A/760, dated 1939, serial 1878, complete with original electrical cord and original Air Ministry-issue box A WWII Air Ministry issued Aldis Signal lamp, 5A/760, dated 1939, serial 1878, complete with original electrical cord and original Air Ministry-issue box](https://auctions.specialauctionservices.com/images/lot/7766/77668_4.jpg?1615217289)
A WWII Air Ministry issued Aldis Signal lamp, 5A/760, dated 1939, serial 1878, complete with original electrical cord and original Air Ministry-issue box
![A WWII Air Ministry issued Aldis Signal lamp, 5A/760, dated 1939, serial 1878, complete with original electrical cord and original Air Ministry-issue box A WWII Air Ministry issued Aldis Signal lamp, 5A/760, dated 1939, serial 1878, complete with original electrical cord and original Air Ministry-issue box](https://auctions.specialauctionservices.com/images/lot/7766/77669_0.jpg?1615217290)
A WWII Air Ministry issued Aldis Signal lamp, 5A/760, dated 1939, serial 1878, complete with original electrical cord and original Air Ministry-issue box
![air traffic control - What is the meaning of a flashing white signalling light in Aldis Lamp? - Aviation Stack Exchange air traffic control - What is the meaning of a flashing white signalling light in Aldis Lamp? - Aviation Stack Exchange](https://i.stack.imgur.com/h3Al9.jpg)