Series connected magnetically operated reed relay switches - use opposite polarity switching to avoid false operation by stray magnetic field

摘要

Reed relay switches are connected in series to form a circuit protected against mis-operation by stray magnetic fields. The arrangement is applicable to door and window alarm circuits. Alternatives are available which use individual reed relays operated by individual opposite polarity magnets or where a switching magnet counteracts the field of a polarising magnet. Two reed relays (1, 2) with slightly magnetised switch contacts are operated when switching magnets (4, 5) are moved into proximity. Where the switching magnet counteracts the field of a permanent magnet. The permanent magnet forms the switch contact itself.