Contract Wall Magnet w. Back Box for Surface Mounting 24Vdc.

Electromagnetic wall-mounted door holder
24Vdc or 230Vac supply voltage
200N - 500N holding force
Surface mounted
Fire-resistant ABC white plastic housing
Built-in release/test button to stimulate alarm activation

Your compatible 24V power supply is available here: RGL 2402/4TRS | 24Vdc 2.0 Amp Power Supply (PSU)

When used in conjunction with a suitable door-closing device, fire alarm and detection system, the Briton electromagnetic hold-open devices permit fire doors to be held open during normal operation. In the event of a fire or smoke detection, the units are automatically de-activated and the doors will close under the normal action of the door closer.

Briton Fire Door Closers | Briton Exit Devices | Briton Locks