|The title is misleading, very misleading for it has nothing
whatsoever to do with submarines. Later on we will meet this S/T
[Submarine Telegraphy] again when it will apply to
submarine communication using the Morse code, the forerunner of UWT
[underwater telephone] and ASDIC/SONAR which detected submarines. Both
this and the S/T sections yet to come, were operated and manned by the
W/T Branch of the Royal Navy.
By 1899 there had been a transatlantic
telegraph cable between Europe and the USA for over forty years. The
earliest of these cables sent messages in hours rather than the weeks or
months taken by ships, and the system was considered God-sent. The
cables laid in the 1860's changed all that and the message were sent in
a matter of seconds. Although the speed had been dramatically increased,
the problem of only one signal at a time caused great backlogs and one
can imagine the frustration of an operator, say in the UK, having to
wait until the US operator had stopped sending before he could send the
next message E to W. Early in the 1870's duplex was invented which
allowed messages to be sent both ways simultaneously, and then in 1874,
Thomas Edison invented quadruplex allowing two messages to be sent at
the same time. The cable carried Morse code, and a good operator
could earn a fortune in bonuses clearing as many messages as possible.
The operator sat listening to the clicks coming through the cable and
the very best could master 40wpm, a mega fast speed let me assure you.
One of the fundamental problems of transmitting a signal through a
lengthy submarine cable was that the electric current tended to be very
low making the signals difficult to detect. William Thomson, a Scot who
became Lord Kelvin, discovered a way of detecting and measuring such a
tiny signal. He of course knew of the Galvanometer which was developed
as early as 1802 and which detected an electric current, but science had
moved on and it was too insensitive to detect currents which were in the
order of one one hundred thousandths [1/100,000th] of a 100W electric
light bulb. He decided to use a mirror and after his success with it, he
called his device a mirror Galvanometer. The Thomson mirror
Galvanometer could detect signals one thousand times fainter than any
other receivers. This device allowed signals passing through submarine
cables to be easily read and seen, for what he quite literally did was
to get the cable signal, raw Morse code, to flash on a mirrored
pin-point light which to the trained eye, could be read rather like a
flashing light sending a signal between two ships.
The cables belonged to the world of commerce, lock stock and barrel,
and had nothing to do with the Admiralty. However, since they were
already laid, might it not be at least prudent to investigate their use
in times of war? This pdf file tells of how a Royal Naval team
went to search out some answers to that question.
This is a piece of paper tape with signals inked on it by a syphon
Problem of the RN having operators who cannot read the
mirror light and the signal it portrays even at slow speeds, even though
these are highly trained operators at great speeds on flashing lights.
Speed of 'mirror speaking' [as coined by the cable men] should be 15 to
Experiments at Penzance.
Which grapnel to use to pick up the cable from the sea
Naval team involved and their findings.
Further trials at sea in a cable laying ship are thought
possible and worthy of the effort involved.
The Sullivan Galvanometer is preferred to the Thomson
A watching-brief is being kept and trials will take
place in HMS Vernon on the suitability and viability of using submarine
cables for warfare communications.