Block Stacking
Up to this point, all blocks of every project were connected sequentially, like beads on a string. This means that an output of one block only connected to a single input of the next block. This doesn't have to be the case. It is possible to connect one block's output to several downstream blocks in a fashion called block stacking.
Access Control 3: Door Sensor & Alarm
The third step in creating a full-featured access control application adds the door open sensor and an alarm relay. Again, a keypad key is used instead of an actual door sensor wired to your TPS' IO line to simplify testing. The F4 key (marked "DOOR SENSOR" on the LCD) stands for the actual door open sensor.