[GreenKeys] Teletype Part Numbers

[Jim Cooper]

On 9 Dec 2020 at 21:55, ad7i wrote:

> I've never understood the concept of
> the pulling and holding magnets for the
> M15. 

Here's a simple explanation. 

The pulling magnets came first ... just as the 
name infers, the current thru the coil PULLS 
the armature up to it ... but it takes a lot of 
initial 'pull' to get the armature moving and up 
to the face of the magnet.  That's one reason 
they run on 60 mA. 

The holding magnet runs on 20 mA because there 
is a cam on the shaft the PUSHES the armature 
up against the magnet face mechanically -- then 
the magnet coil current only needs to HOLD it 
there against the face until the current stops. 

Jim  W2JC