The 40SUA or 40-SUA from Cossor is a half wave rectifier to complement their range of 13 Volt 300 mA heater based valves. This range was designed for sets without a mains transformer that would operate on 240 Volt mains AC or DC. In the UK DC mains supplies were still present in some areas in the early 1930s.
The heater connects are clearly separate from the cathode connection.
The cathode tube is round and the anode is much wider than the front to back dimension.
The classic envelope is 44 mm in diameter, and excluding the B5 base pins is 99 mm tall.
Reference: Data-sheet. Type 40SUA was first introduced in 1934. See also1934 adverts.
