On Mon, 20 Aug 2007 12:35:20 +0100, "Ron(UK)"
wrote:

Ross Herbert wrote:

Here is a typical 3000 type telephony relay as used in UK and
Australia in SxS. http://www.britishtelephones.com/autorel.htm

In fact this particular picture appears to show the winding bobbin
with a copper front cheek which is the smallest armature end slug
of
all.


The common GPO 3000 had the copper slug embedded into the armature.

No Ron, the 3000 type relay armature was fitted with a small brass
residual stud to ensure the armature was not unduly held by residual
magnetism in the core on releasing, NOT a copper slug. Impulsing
relays used an adjustable residual stud (brass screw and locking nut)
so that the residual gap could be set according to specific
requirements.

Here is a pic of a 3000 type relay with a 1" heel end slug and an
adjustable residual stud.
http://www.englishclocksystems.co.uk/slugrelay.html