analog robots are driven by electrical signals that results from the physical properties of the electronic components and the way these components are wired up. in contrast to digital robots no program with instructions is executed.
the inspiration for this kind of robots comes from the nervous system of organisms. probably the first analog robots were wiliam grey walters turtle robots named elmer and elsie. in his book vehicles experiments in synthetic psychology valentino braitenberg sketches in several thought experiments how one could build vehicles that exhibit complex behaviors like light-searching just as a result of wiring up sensors with motors and with simple thresholding units (neurons) in between. marc w. tildens beam robots are instantiations of robots based on these principles. we like the beam circuits because they render an abstract concept concrete: you can create an autonomous light-searching robot with just four transistors, four resistors, two diodes, two capacitors, two solar panels and two motors or a walking robot that exhibits different walking patterns out of four inverters, four resistors, 4 capacitors, a battery pack and two gearbox motors.