Every information provided is based on the tested devices.
MCU04607129 Working at 27.145 MHz in combination with several others from Logitech, sold in Germany. The cordless devices seem to cycle through a fixed set of codes every time you press 'connect' and the receiver seems to lock in on the first code he receives undistorted. They simply seem to run out of the fab and the customer connects them the first time he is using the set, according to the manual. This leaves the cruical backdoor to connect whatever device you have to whatever receiver you have. The receiver waits for 30 minutes after initialising a connect for new devices to sync to them, even if there has been an undistorted reception of at least one sync-code.