Soviet A-109 counting tube. The A-109 (along with the A-108 and A-107) is the smallest dekatron ever made.


Soviet A-107 counting tube in operation. Note that the glow transfer is completely invisible under normal lighting conditions, the A-107 is not a direct-view counter and the counting loop is covered with opaque silvering.


Soviet A-108 counting tube mounted in a YS-650 demonstrator module.


Soviet A-108 counting tube in operation.


A-109 counting tube in operation. It should be noted that getting the mixed-gas A-109 tube to count reliably is no easy task; the A-108 is a much more stable tube for most applications.


Miniature dekatron size comparision. Part numbers from left to right:Elesta EZ10A, Westinghouse 6879, Sylvania 7155, Elesta ECT100, Soviet A108, Soviet A109.


This is the recommended Soviet circuit to operate an A-108 or A-109 as a base-10 counter. Even and odd cathodes are driven from a flip-flop such that only a single cathode is lit at a given time.