On 30/05/2016 00:15, Bob Wilson wrote:
On 5/29/2016 4:39 PM, gareth G4SDW GQRP #3339 wrote:

Suddenly it has clicked after setting up the IC728 for Jim - the reason
that some Morse keys had a shorting switch must have been to
provide a continuous key-down position for tuning the TX and ATU!

At least in the US:
The switch, e.g. on a J-38 key from WWII, dates from before there were
tube circuits to be peaked or dipped! On the old telegraph lines, the
ancestors of current loop circuits, all the keys and sounders on a large
network were simply in series, with a battery also in the circuit. If
your key were open, then nobody else could "talk". So you had to short
the key when not actually sending. And of course as soon as a switch
like that is a "tradition" it is likely to appear on devices long after
that need has disappeared.

Bob Wilson, WA9D

(I think Gareth really meant that as a complaint about some of the
always-key-down operators, and I would agree! But I could not leave it
alone.)

Another reason for a shorting switch was so that the transmitter could
be left sending for DF purposes while the aircraft crew bailed out and
awaited rescue.

--
Spike

Many persons have a wrong idea of what constitutes true happiness.
It is not attained through self-gratification but through fidelity to a
worthy purpose - Helen Keller