Ulf, The new A9 was only installed in units that had the 10811 installed so HP was not concerned with it working with the 105 oscillator. In the 10811 interface the EFC from A9 goes thru a 316K resistor to a 147K (nominal) resistor to ground. This forms a voltage divider the feed the 10811 EFC pin. So the peak EFC the 10811 feels is much less than the A9 output! Cheers, Corby