The Lloyd's Signal Stations Act 1888

This Act conferred on Lloyd's the power to establish signal stations with telegraph communications.
In the Highlands and Islands we find the following from the census records:

1891
Edward Robinson, 26, Lloyd's Signalman, Lloyd's Signal Station, Barvas, b. England
Caroline Robinson, 20, Wife, b. England

George Simpson, 30, Signal Officer (Lloyd's), Dunnet Head signal Station, b Dunnet, Caithness
Barbara M Simpson, 23, Housekeeper, Sister, b. Dunnet, Caithness

1901
William Thomas, 28, Lloyd's Signalman, Lloyd's Signal Station, Barvas, b. England
Margaret Thomas, 16, Wife, b. England

George Simpson, 40, Lloyd's Signal Officer, Dunnet Head, b. Dunnet
Jessie Simpson, 28, Wife, b. Canisbay, Caithnessshire

There is a description of the remains of the Dunnet Head station here: Dunnet Head whilst this (pdf) of an archeological landscape survey of Ness records the location of scattered remains from the butt of Lewis station: Butt of Lewis

Harry Hawker's failed attempt to fly the Atlantic in May 1919 ended when he and his navigator, Kenneth Mackenzie Grieve, were forced to ditch in the sea. They were picked-up by a radio-less ship, the Mary, so when they reached the Butt the Mary signalled the Lloyd's Signal Station:

Lloyd's signal station at Butt of Lewis telegraphs this morning as follows:
Danish steamer Mary passing eastwards signalled following:
'Saved hands Sopwith aeroplane.'
Station signalled: 'Is it Hawker?'
Steamer replied: 'Yes.'

Thus the Butt of Lewis was able to let the World know that the airmen were safe, six days after the ditching of the aircraft...

I have been sent this interesting link that includes images of the Dunnet Head Station: Naval Onshore Signals
and a brilliant blog from Caithness that I follow:Mary-Ann's Cottage