Aluminium cased telephone speaker standards

[ScottBouch]

Hi all,

In the attached images you will see on the left the speaker from the handset of a 746 telephone, next to it on the right is a speaker from a MK4A flying helmet headset.

The telephone speaker is a nominal 45mm in diameter, and the helmet speaker is a nominal 40mm in diameter.

Apart from the size and electrical differences, they follow the same form, case with recess for two terminal posts.

Now, does anyone know where these standard forms and dimensions are defined? Is it a GPO / Ministry of Supply standard, or BS etc...? are there standards for the electrical characteristics too?

I'd love to gain some proper understanding of this type of speaker casing, and the origins.

What companies manufacture speakers to these standards?

Many thanks, Scott

[G6Tanuki]

The ones I remember were made by A.P. Besson, who later became Besson Hosiden.

[Nickthedentist]

Seconded.

The GPO ones usually have a manufacturer’s code stamped on them.

[ms660]

Item on the left in 2nd photo, TMC, Bathgate, West Lothian.

Lawrence.

[Roger Ramjet]

Originally Posted by G6Tanuki

The ones I remember were made by A.P. Besson, who later became Besson Hosiden.

I have come across burglar alarm sounders that use a similar earpiece receiver powered by a 12v oscillator. These were known as BESSON BANDITS so me be part of same family ?

Rog

[ScottBouch]

Brilliant, you guys have pointed me in the right direction! thanks!

"Rocking Armature Transducers":

https://www.royalsignals.org.uk/inse...inserts_en.pdf

I have seen Besson on the back of some of the flying helmet speakers, this now makes a lot of sense.

Searching online for Rocking Armature Transducers there seem to be a few 'made in China' alternatives out there too.

Many thanks, Scott

[ms660]

A.P. Besson codes, DAD and DAE.

Lawrence.

[ScottBouch]

I have just eyeballed a few of these ex-military ones, and few are marked with A.P. Besson, some with NSN: 5956-99-620-5675, some with other codes.

I guess the customer can specify whatever markings they want!

[McMurdo]

It's Hosiden-Besson, when AP Besson became a subsidary of japanese giant Hosiden.
My workshop internal alarm sounder is a Besson Banshee, and uses one of the earpiece-style inserts, as many industrial sirens did. Some GPO switchboards and 700-series phones used DC bleepers in the same casing.

[dagskarlsen]

I do not know these well! Still I have measured out DC resistance from around 40 ohms up to several hundred ohms. Cant remember how much, but at least more than 200 ohms.

[Nickthedentist]

https://www.britishtelephones.com/menureci.htm

https://www.britishtelephones.com/gp...recin4t_02.jpg

http://www.samhallas.co.uk/repositor...telephones.pdf

[ScottBouch]

Hi Nick, that information is fantastic, thank you!



Funny how those are two websites I've come across during my aviation based research where certain parts (such as some particular relays I was researching) were common to the Air Ministry and the GPO.

Cheers, Scott