Abstract: Door operator for commercial and domestic use with swing-mounted doors are disclosed. Each operator employs a variable-speed d.c. motor as prime mover, and a vertically oriented door-driving operator output shaft journalled in a transmission having a compact transmission housing which includes shock mounts for mounting of the transmission housing and operator within structure associated with the door. The transmission provides speed reduction coupling of the motor drive shaft to the operator output shaft with substantially right-angled relationship between their axes of rotation. The transmission includes a drive gear, to which the motor drive shaft is coupled by miter gear arrangement of different types, with the drive gear in coaxial relation with the operator output shaft but independently rotatable about it.