The Honeywell PRO51BTM is a 3/8” diameter recessed contact with a rare earth magnet. Unlike the Honeywell 944TRE recessed contact, which uses staggered screw terminals, the PRO51BTM uses wire leads to make the connection to your zone wiring. Both recessed contacts are similar and use the special rare earth magnet so you can choose between the screw terminals and the wire leads to suit your preference. However, the PRO51BTM is only available in one color. The full part number for the white colored recessed contact is actually PRO51BTMWH.
The PRO51BTM recessed contact can be used to protect any opening. More often than not, you will use a recessed contact to protect a door or a window. Many people prefer recessed contacts over surface mount contacts because they are more discreet. As the contact and the magnet are drilled into the door and window, they are not visible and do not take away from your home’s decor. However, recessed door and window contacts have a more involved installation as you will need to drill the holes for the contact and the magnet. When drilling your holes, make sure that they are aligned so that the contact is directly across from the magnet when the door or window is closed.
The Honeywell PRO51BTM has a Form A, SPST, normally closed internal reed switch with a contact rating of 100mA at 28VDC. When the rare earth magnet is within the 1/2” magnet spacing gap of the contact, the contact is energized and in a normally closed state. When the door or window opens, the magnet is pulled away from the contact and the internal reed switch changes to the open state which triggers an alarm at your alarm control panel.
You will need to drill a 3/8” diameter hole into your door or window frame to install your PRO51BTM recessed contact. After connecting the alarm wire to the wire leads coming out of the backside of the contact, push the PRO51BTM into the drilled hole until it is flush with the door or window frame. Next, you will need to make a smaller hole directly across from the contact in the actual door or window. Press the rare earth magnet into the hole and insert a screw in the hole in the magnet. As the hole is concave, the screw should be flush with the magnet for a nice smooth finish.