Re: What kind of sensor did I see today?

[Nomen Nescio <nobody@xxxxxxxxx>]

Jim said:

>Lacing wire goes back to the 1800's When Edwin Holmes was doing alarm
>installations.

One of the earliest applications for lacing wire was the protection of
safes.   I believe it was Holmes who pioneered the use of the safe cabinet,
a custom-built wooden cabinet that surrounded the safe.  Penetrating the
walls of the cabinet resulted in a broken wire, causing an alarm before the
burglar even reached the safe.

Safe cabinets were still used up through the 1950s and even later,
sometimes with foil linings instead of lacing wire.  The cost of
construction made them unattractive, as did the availability of electronic
safe protection systems.

>Up until about the mid to late 70's, photoelectric beams
>were large devices using automobile bayonet style light bulbs,
>projecting visible light through a glass lens.

I think it was Arrowhead that introduced the first solid-state photocells
in the early 1970s.  But I do remember the old beams with light bulbs
inside, complete with a spinning metal disk with holes in it to "modulate"
the beam.

- badenov