I'm looking for the simplest monostable to provide a short pulse to
momentarily close a contact on our electric gate at work. Normally it's
opened with remote control but for visitors during office hours is was
equipped with a bell push for entry and exit, this being cheaper than
induction loops etc.

Some wag has found that if the outside button is depressed and held down the
gate cycles through open to closed and then will not accept input from the
other button or the remotes.

I'm after a simple way to have the bell pushes close the contacts
momentarily and then release even if the bell push is held down.

I've got a Crouzet MUR1 that I can get to do the job but it's about 30 quid
and I wonder about something simpler?

AJH