Marconi Guillotine Morse Key

[Ham4CW]

Here's a photograph of my Marconi Guillotine Morse Key. It's not an original, but a high quality copy made by G0NVT in England. It cost only a fraction of what a genuine Guillotine Key could cost, they sell for many thousands of pounds very often!

All we need now is a spark transmitter to go with it!

 

[MI0PYN]

Is the guillotine bit a shorting bar?

I never actually quite got what a shorting bar was for, I get it simulates a permanent keydown, but I fail to see why that is useful. Have I missed something?

 

[MI0PYN]

So it seems that the answer was in the board title "Vintage Telegraph Apparatus".

In use for CW on a radio, it's not really of any use except maybe for tuning if you don't have a "Tune" button on your radio.
However, in old wire telegraphy, apparently they used a normally closed circuit, with the earth acting as return path, and having the shorting bar closed essentially put the station into receive mode, and allowed the opening of a shorting bar to place a station into transmit, and the key to be used to energise the sounders in all other stations. That's genuinely fascinating, and a good example of how technology moved so quickly (from wire to wireless) and made some aspects of the procedures and equipment obsolete.

 

[Ham4CW]

Another use I read about for the guillotine bar was to disconnect the power to the spark transmitter if the key contacts fused together. A kind of manually operated circuit breaker!

They're odd Morse Keys in that you have the usual set of contacts, there is the guillotine contact (more of a heavy duty breaker), and there is a third set just off to the side of the main arm. The third set switches at the same time as the main set. The copies that G0NVT makes are astounding. In fact all of his keys are!