Source: Welcome to Smart Home with QIVICON – QIVICON

Douglas Carl Engelbart (January 30, 1925 – July 2, 2013) was an American engineer andinventor, and an early computer and Internet pioneer. He is best known for his work on founding the field of human–computer interaction, particularly while at his Augmentation Research CenterLab in SRI International, which resulted in creation of the computer mouse, and the development of hypertext, networked computers, and precursors to graphical user interfaces. These were demonstrated at The Mother of All Demos in 1968. Engelbart’s Law, the observation that the intrinsic rate of human performance is exponential, is named after him.
https://en.m.wikipedia.org/wiki/Douglas_Engelbart

https://en.m.wikipedia.org/wiki/Stewart_Brand

L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz).

Source: L band – Wikipedia

This tutorial is going to teach you basics on using Optical Dust Sensor.

Source: How to Interface With Optical Dust Sensor: 9 Steps (with Pictures)

Source: RFM12B-S2 Wireless Transceiver – 434MHz – WRL-09582 – SparkFun Electronics

Source: Cheap 433MHz Transmitters | Majenko’s Hardware Hacking Blog