24b-610

[val]

Does anyone know when exactly those "three screw" Dfh.a / 24b-610 headphones

were phased out and those new "four screw" Dfh.a we all know were introduced?

https://www.radiomuseum.org/r/mil_doppelfernhoerer_dfha24b_610.html

Gerätliste D97/1+ from 1.7.1943 states that 24b-610 is Doppelfernhörer Dfh.a,

so code and designation remained the same, only design was changed.

[Funksammler]

I think this is just a design variation, slightly different from the prewar Telefunken/Siemens etc. design. Around 1937 a lot of new equipment was phased in, the Torn.E.b, Torn.Fu.b1, d2 etc. so the equipment standards crystallised around that time. They must have thought the extra magnetic circuit added some power to the headset, but it seems it was dropped shortly afterwards as an unnecessary manufacturing complication.

regards,

Funksammler 

[val]

Thanks @Funksammler. So far i have seen "three screw" versions from 1937 and 1938.

Does anyone have later ones to show?

[val]

Nice detailed images of '37

https://myvimu.com/exhibit/87395-sluchawki-polowe-1937

[val]

@Funksammler - earliest "four screw" headphones i have seen is dated 1940.

This makes 1939 very strange year - haven't seen neither "three" or "four" screw

variant of that year yet. Hopefully something will come out...