That first book is one of the "Imperial Army Series" by "Captain E Solano", and quite how he got away with it has always puzzled me - it's "Based on Official Manuals" but I'm sure if it was done today he'd disappear under a pile of lawyers and never be seen again.
In the beginning it was all couriers (on foot, horseback, bicycle, etc.) plus carrier pigeons for physical message transfer, with visual signalling (flag, lamp & heliograph) and fixed telegraph (semaphore and railway telegraphy) systems.
A couple of early manuals are:
1887 Manual of Instruction in Army Signalling
1896 Signalling Instructions, Gen. No. 1563
After that, there's "Signalling Regulations 1904" and the Indian supplement to it.
The next change was the small, almost square, pocket book "Signalling Training" Part I was for the regular army and the Part II book was for the Reserve and Militia (I think - they're all boxed up at the moment. They were regularly reprinted/updated, e.g. 1907, 1911, 1915 (from memory, again).
These were intended for the signallers in the actual fighting forces (Infantry/cavalry/Artillery).
In parallel with those, there was a two volume set "Instructions In Army Telegraphy and Telephony" Vol.1 (1nstruments) 1907/1914 and Vol.2 (Lines) 1908/1916 which are considerably more technical and intended for the R.E. Signal Service.
The European War (Great War, WWI) saw very rapid advances in communications technology, and the pocketbooks were rapidly outdated.
The next set was a series of 8 pamphlets, issued between 1917 and the early 1920s, entitled "Signal Training" (Part 'n' and the subject covered).
Signal Training, Part I, Visual Telegraphy, October 1917
Signal Training, Part I, Visual Telegraphy, May 1919
Signal Training Part II (Provisional), Methods of Intercommunication (Other than Visual) Employed in Forward Areas, November 1920
Signal Training Part IV (Provisional) Line Telegraphy and Telephony (Lines) 1922
Signal Training Part VI, Procedure, Sept 1918
Signal Training, Part VII (Provisional), Signal Organization, 1921
Signal Training, Part VIII (Provisional), Intercommunication in the Field, Feb 1920
(As you can see, I'm missing Part III (Which I think is Line Telegraphy and Telephony (Instruments), and Part V - let me know if you ever see an affordable copy of either of those.)
That set basically collected up everything that had been learned up to the end of WW1.
Sometime later a new set began to appear, and this was divided into the non-technical (for the army as a whole) and the technical side (for the Royal Corps of Signals).
The basic signalling skills series was "Signal Training (All Arms)" initially published as a bound volume (Softcover/Hardcover), and existed in 1928, 1932 and 1938 editions.
The technical side was covered by a series of six volumes "Signal Training" which carried on from where the "All Arms" book left off:
Signal Training Volume I, Organization and Inter-communication in the Field, 1926
Signal Training Volume II, Part I, Theory of Electricity and Magnetism as applied to Telegraphy and Telephony, 1923
Signal Training Volume II, Part II, Theory of High-Frequency Currents as applied to Wireless Telegraphy and Wireless Telephony, 1924
(I don't recommend reading this one, it's still thinking in terms of the luminiferous ether.)
Signal Training Volume III, Pamphlet No. 'n'
Volume III was a series of pamphlets on specific items of equipment. They stopped numbering them at (I think) No.33 (the WS18) during WW2 and un-numbered ones exist so the series carried on.
Signal Training Volume IV, Construction and Maintenance of Lines, 1927
Signal Training Volume V, Part 1, Training of Signallers, Signal Office Practice, Visual Telegraphy Procedure, 1927
Signal Training Volume V, Part 2, Line Telegraphy Procedure, 1927
Signal Training Volume V, Part 3, Wireless Procedure, 1928
I don't have the next one, as it was classified "Security", but have read the copy at Kew:
Signal Training Volume VI, Fixed Signal Services.
(Basically camps, fortresses, coastal gun positions, and what became the Defence Communications Network.)
In the mid to late 1930s, the series was revised (Volume III just carried on):
Signal Training Volume I, War and Training, 1937
Signal Training Vol II, Part I, Electricity and Magnetism, April 1935
Signal Training Volume II Wireless 1936
Signal Training Volume II Wireless, Part II Supplement, Skip Distance Graphs for Short Wave Signalling, 1936
Signal Training Volume II, Part III, Line Telephony and Telegraphy, 1936
(Vol III continues with the "numbered" wireless sets, etc.)
Signal Training Volume IV, Construction & Maintenance of Lines, 1927, amended to 1941 (This is severely cut down from the 1927 edition.)
Signal Training Volume V, Signal Office Organisation and Procedure, 1932
Signal Training Volume V, Signal Office Organisation and Procedure, 1938
With the arrival of WW2 everything was changing rapidly and there was no time to revise/reprint/reissue bound volumes, to say nothing of the waste of resources involved, so just about everything turned into pamphlets that could be updated and issued more easily and cheaply.
Signal Training (All Arms) split into 12 sections (I assume Pamphlet 11 was classified because I've never seen it!)
1 - Signalling Codes
2 - Visual Signalling
3 - Electricity and Line Signalling
4 - Wireless Signalling
5 - Signal Procedure
6 - Procedure for Artillery Fire Orders
7 - Originally for communicating with balloons, etc. (Never seen it!)
8 - Signal Office Procedure
9 - Training
10 - Tactics (a series of pamphlets for various arms of the services)
11 - Unknown, probably crypto.
12 - Communication Security
The "Signal Training, Volume x" set also gained update pamphlets:
1 - Construction & Maintenance of Lines (1940/1942) later renumbered to '4"
2 - Wireless (frequency allocations, etc.)
3 - Maintenance
4 - Lines
5 - Signal Office Procedure
6 - Still "Security/Confidential/Secret" - Jamming, Countermeasures, Deception.
7 - Training
8 - Procedure (switchboard & Teleprinter operating, etc.)
9 - Cryptography, I think - still Confidential/Secret
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In addition to that lot, there were reference cards: "Do's & Don'ts of Message Writing", "How are your Batteries", Netting Drills, Signal Procedure, etc., etc.
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Also (around late 1942) the Signal Procedure changed dramatically. This was the introduction of the "Single Callsign Procedure" still used today, and is basically the WW2 German signal procedure with the serial numbers filed off and a coat of Khaki/Green O.D. paint applied. (After the discovery that the existing British signal procedure, with repeated callsigns at start and end of the message (so that both ends knew who they were talking to) was an absolute gift to enemy intercept operators.)
Finally: the Phonetic Alphabet changed dramatically: from the original seven letters of the 1904 regulations (A, B, M, P, S, T & V) through to the Ack, Beer, Charlie, Don of early WW2, the 1943 version to standardise it with the USA, the 1952 "Inter-service" version, and finally the (1955) NATO alphabet used today. (Aside: The Canadians had a separate phonetic alphabet for their French-speaking units, just to make life even more complicated.)
Hoping this is useful (or at least interesting).
Chris.