There is a setting for the 1750/1 Miro monitor which means that the door will open as soon as the handset has been called, without the user needing to answer or press the door open button.
If the LED at the bottom of the monitor is flashing green, then the automatic door open function has been activated.
To turn this function off -
Press the button with one dot next to it for 5 seconds to enter programming mode.
The LED should now flash yellow.
Press once the button with the 'key' symbol.
Press the button with one dot next to it for 5 seconds to exit programming mode.
The LED should not be lit.