The book contains nearly eighty illustrations. Many of them have been created specifically for the book. Santosh Hombal has kindly taken time off his busy schedule to create many of these illustrations. Some are drawn from original sources. Copyright permission have been obtained where necessary. On this page is a sample of illustrations appearing in the book. You may click on an image for a larger version.

A Framework for Digital Technology

Gray’s Caveat and Bell’s Notebook Sketch
(a) Drawing in Gray’s caveat of February 14, 1876, shows the workings of the liquid transmitter. (b) Bell’s laboratory notebook reproduces a similar sketch dated March 9. Such a design does not appear in his notebook before March 8.

Pupin’s Inductive Loading of Transmission Lines
(a) Pupin draws an analogy with vibrating strings by showing that an unloaded string suffers signal attenuation. (b) A string loaded with point masses achieves maximum transfer of energy. (c) Loading coils placed at regular intervals on an electrical transmission line achieve the same effect. (d) Pupin’s toroidal coil. Source: (Pupin 1899, fig. 3, 7, 10, 11, 12).
Pupin, M. I. (1899). “Art of Reducing Attenuation of Electrical Waves and Apparatus Therefor,” US Patent 652,230, filed December 1899, granted June 1900.

Digital Modulation Waveforms
(a) QPSK modulation shows sharp phase transitions of 180 degrees. (b) OQPSK limits such transitions to 90 degrees, though they may occur more often. (c) In-phase of MSK waveform. This is shown along with its input bits. (d) Quadrature-phase of MSK waveform. This is shown along with its input bits. (e) MSK, combined from (c) and (d), has constant envelope and continuous phase transitions.

Applications of Error Detection and Correction
(a) Such barcodes are commonly found on everyday products. In this example, 13 digits are used. The first digit, 5, represents the method of encoding digits as strips of black and white lines. The last digit, 7, is parity. (b) Such QR codes are used to refer users to websites. In this example, the word Wikipedia, while being artistic, destroys some of the original information. Despite this, scanners can read the data correctly because of error correction. Source: Qrc-designer, Wikimedia Creative Commons.

Baker’s Map Applied to an Image
(a) Baker’s Map stretches, slices, and stacks equal parts. (b) Original image of Peppers. Copyright ownership is unknown. (b) Five iterations of Baker’s Map renders the image unintelligible. Image appears like noise. This has relevance to cryptography to protect private data.

Layered Protocol Design for the Web
Protocols are designed layer by layer. HTTP is used at the top between web servers and clients. To carry them over the network, HTTP messages are broken up and packaged into TCP/IP packets. The receiving end reconstructs the original HTTP messages. Actual user data carried by HTTP can be text, images, video, or audio.

The Experiments of Heinrich Hertz
(a) Initial experiments involved a secondary circuit connected by an inductive coil to the primary sparking circuit. (b) Later experiments showed that sparking occurred even when the secondary circuit was completely disconnected from the primary. This was a clear indication that sparking produced electromagnetic radiation. (c) Secondary circuits of different shapes and sizes were tried at different distances from the primary circuit. (d) Hertz’s own diagram showing how electromagnetic waves disengaged themselves from the primary circuit and travelled outwards. Source: (Hertz 1893, pp. 34, 37, 104, 144).
Hertz, Heinrich. (1893). Electric Waves, Transl. D. E. Jones, New York: Macmillan and Co.