Wednesday, May 20, 2020

#Automation: Sending Signals Over Wires.

Crystal oscillators are a piece of automation that are ubiquitous but barely noticed. They are the basis of both computers and the internet. In computers they play a role analogous to the prime mover in a factory, and in networking/communications they do the code keying-in at magically fantastic speeds.

When telegraphy was invented, signals over wires were manually keyed in with telegraph keys, with an average speed of about 150 characters/minute. No wonder telegrams cost so much, which in turn spawned a new language form: telegraphese.
A typical telegraph key.
Today the internet depends on network interface controllers which use crystal oscillators to do the keying in, at about 750 million characters/minute (100 Mbits/sec).
The metallic cubical box, to the left of the large chip houses the crystal oscillator on this 25 Mbits/sec networking card.
The metallic box opened, showing the quartz crystal slice.
The following video explains how a typical quartz watch works in an easy to understand way:



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