Tag: current

Mains Extension Cable Safety Issues With UK 13 Amp Plug

Introduction

There are three Mains Extension Cable Safety issues covered in this post which are:

  • A UK 13 Amp Mains Extension Cable Safety Issue where socket can become dangerously exposed. I came across it by chance when I landed on the PlugSafe site. I’ve linked to their site in this post so you can see what they have to say about the subject. I’ve also produced my own pictures depicting the problem so you can see what I’m referring to. Full credit to PlugSafe for making us all aware.
  • A fire risk due to overheating of coiled up mains extension cables when used for heavy loads.
  • A risk of shock when using old 13A plugs which don’t have insulated pins for Live and Neutral connections.
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Morse Code

History

Morse Code was devised by Samuel Finley Breese Morse, an American artist and inventor, in the 19th century. It is made up of a series of dots and dashes when written down.

Speaking Morse Code

When spoken a dot is pronounced “dit” if it is the final element of a character, else it’s pronounced “di”, and a dash is pronounced “dah”. e.g. “C” [ — · — · ] = “dah-di-dah-dit”.

Transmitting Morse Code

1.  By Interupting A Light Beam

If Morse Code is transmitted as a beam of light then the transmitting light often has a shutter in front of it which is opened by means of a lever to let the light out. Historically this is because the persistence of electric lights is too long if they are turned on and off by electrical means.

2.  By Using An Electrical or Radio Signal

If Morse Code is transmitted as a radio signal, or current down a wire, then the signal is controlled by a special electrical switch known as a Morse Key or Telegraph Key. In its simple form this is an ON/OFF switch, but in its more complex form it is a changeover switch. With the changeover switch in one position it sends a series of dots and in the other position it sends a series of dashes. The timing of these is electronically generated. The operator leaves the key in the central position (the default) when not transmitting and moves the key from side to side to send the necessary dots and dashes while listening to his output on headphones. By this means the operator can send a fast signal with fewer movements of the wrist.

When transmitted as a radio carrier wave, light or electrical current a dot is a short burst of radio carrier wave, light or current, and a dash as a burst of radio carrier wave, light or current with a period three times as long as a dot.

The period between a dot/dash and the next dot/dash within the same character is equal to the period of a dot.

The period between characters is equal to the period of a dash.

The period between words is the same as seven dots.

Morse Code
Table of Morse Code

Ref. http://en.wikipedia.org/wiki/Morse_code#Development_and_history