of any parts fig2 is diagram showing the one wire key pad in this configuration using the same microlan u2122 a key pad can be configured either in parallel or in a matrix configuration such as in a regular telephone in the schematic shown when a switch is depressed that particular serial number ds2401 or 1990 is brought on the bus assuming the bus is active meaning the data line is held high the device will issue a presence detect signalling to the host pc or lock electronics to go out and look up which device caused the presence detect each device can correspond to one number of an array where two devices could correspond to a particular button that was pressed it should be noted that it is not shown in this schematic but a ds2502 could be used as a directory to give a correlation as to what button or serial number for each 2401 is and what the corresponding serial number or serial numbers corresponding to the button pressed is this will allow you to take this device and plug it on to any one wire bus such as the main system configuration 100 or 1000 that is shown and the 2405 will have a file structure such as described for the door controller modules where there is an f map function.