A releasable door hold-open device or assembly is mounted on the header over a door panel. The assembly has a track channel with a top web and depending flanges. A door panel connector arm has a traveller movable in the track channel. A solenoid operates a detent in the track channel near the hinge end of the traveller path. A conductor channel is fastened to the top web and communicates with the track channel through an opening. A connector block releasably adjoins the track channel and the conductor channel at the hinge end thereof. A smoke detector underlies the connector channel at the other end of the track channel. Conductors from outside extend through the connector block, through connecting plugs in the block and track channel and to the solenoid and through the conductor channel to the smoke detector.