Scanner device type - manufacturer independent.
An 'xcmHrDeviceScanner' device with 'xcmHrDevInfoRealization' of
'physical' is a 'real' input device (eg, a 'scan channel' on a
multifunction printer).
An 'xcmHrDeviceScanner' device with 'xcmHrDevInfoRealization' of
'logical' is a 'virtual' input device (eg, a 'personality' of a
'scan channel' on a multifunction printer).