It is also probable that the relay design was based on impirical practice since no mention of any calculations is made, but there are several references to trial and error such as the number of turns of wire and size of wire used.
The Letters of Patent No 10,549/1914 – Improvements in Relays connected with Electric Signaling in Mines and the like - was applied for on 29 April 1914, the complete specification was left with the Patent Office on 27 October 1914 and the Patent was granted on 29 April 1915.
However, it is surmised that in order for the technical aspects of the relay design to be looked upon with favour by the Patent Office Examiner, bearing in mind the questionable electrical qualifications held by Henry Davies, the name of the General Manager of G.E.C. was added to the patent application thus making it the Davies-Railing relay.
On 5 May 1915 Dr Atkinson, Divisional Inspector of Mines. Mr Faraday Proctor for G.E.C. Cardiff, Mr F LI Jacob, General Manager of WW & Sons Ltd, Mr Atliron, Assistant General Manager and Agent in Ferndale Offices witnessed tests on a Davies-Railing Relay and in their letter dated 6 July 1915, G.E.C. advised Henry Davies that they had an order for 76 relays. This was followed on 2 September by an order for 2 four-poled relays from Nixons Navigation Collieries.
Further orders for four relays for use at Nos l & 5 and Nos 2 & 4 Pits, Ferndale, and one in the sum of £4/15/0 for the Ffaldau Colliery Company, Pontycymmer soon followed.
In their letter to Henry Davies dated 27 March 1917, G.E.C. advised that over 100 relays were in use in the South Wales coalfield.
During the coal strike in September 1921 he delivered a relay to Mr Charles Jones. This relay was made specially to work on telephone lines from the Power Station to Mr Jonses's house. Resistance 1150 ohms. It was very efficient but never fixed up. Two other relays had been altered to work on Power Station phones in May & June 1921 during the strike time.
In 1908 a royalty of 4/- per coil was paid.
In 1915 a royalty of 10/- per instrument was agreed on the proviso that the selling price of each relay did not fall below £5.
In 1928 an entry in Henry Davies’s diary advised that the total royalties earned from the sale of relays was £583/1/11. In today’s money, assuming that on average the value of money halved every 10 years, this would be equivalent to approximately £500,000.