First World War Communications

 Communications during WWI were pretty rudimentary.

The mainstay was the runner who braved bullets and shells, mud and mayhem, to take messages to and from forward positions and the rear. Although telephones were relatively commonplace they relied on wires which were easily cut by shellfire or accidental damage. Less common was radio, and this was used both on the ground and in the air especially during the latter stages of the conflict.

A prime use for the telephone was from very vulnerable forward positions acting as observation posts for the artillery positioned some distance away and it was usually not a very happy soldier who was told, in the face of shellfire and rifle bullets, to trace and repair breaks in the wire.

It was not uncommon for a battle to be begun on the strength of orders originating many hours or even days earlier. When no instant communication was available it placed a front-line commander in an impossible position. He could not delay an advance even though it was outside the bounds of reason to proceed. Because of this sort of position the introduction of radio to the battlefield proceeded apace and by the end of the war quite sophisticated equipment was being used.


 In the environment of a trench it was a trifle uncomfortable when it came to operating a transmitter. Here an NCO, festooned with cables is using a medium power trench set precariously balanced on a packing case covered with a piece of canvas.

 Trench Transmitter

Made by Lavington of London S W

Unit HT WT 30 WATT MARK I No.2563


 This was described by the vendor as a morse key for a 30watt Trench Transmitter.

Not a simple morse key however as you can judge from its picture!

Or if you could feel how heavy it is!

From what I can gauge from the circuit and instructions,on its lid, the trench transmitter had two main parts. The first is the actual transmitter carrying the valve(s) and the tuning components. The second is the box of tricks depicted here.

Inside is a large, heavy transformer with a 10 volt primary winding and a high voltage secondary (yet to be measured).

Primary current is interrupted by the small springy key in the centre of the inset wooden case. Under the key is an iron core energised by current passing through the transformer primary winding. The device in the centre with the springy key is therefore a buzzer which interrupts the primary current at an audible rate generating an instantaneous high voltage in the valves HT line, generating RF output.

The polished wooden compartment on the left of the lid contains a spare spring and various spare terminals.The leather strap was probably used by a soldier for securing the box to his leg so that when comfortably seated he could operate the transmitter. That is until his leg went to sleep from the pressure of the box!

The strange looking flaps fastened to the box lid are a simple waterproofing arrangement. When new these were stapled down to the wood but when first used the edges were torn away and then loosely dropped down when the lid was closed. This kept out the mud and rain as of course the operator had often to brave dripping mud from the corrugated iron roof of a hole in the side of a trench.




 This label tells the operator how to connect and check the operation of the wireless click to see a bigger picture

 This label gives the wiring details click to see a bigger picture

 Top view showing the interruptor for converting DC to AC for the HT transformer click to see a bigger picture




The two wires connected to the buzzer connect to the black-covered flexible lead with the plug labelled "10 VOLTS" . My guess is that 6 volt and 12 volt accumulators hadn't been standardized at the time this power supply was designed. The plug is stored by pushing it into the ebonite block in the lid and over the years the cable has become stiff and brittle and has lost some of its rubber covering. The connection marked "T.V.T" is a mystery but may stand for "Transmitter Valve Trench". Was the output keyed by a proper morse key ?

Is the box an arrangement for applying amplitude modulation (MCW) to the transmitter which is then keyed by a key plugged into the transmitter front panel?







 Above: could the leather strap be for securing the box to the operators upper leg, perhaps to ensure it was kept tolerably dry? Below is a set of spare parts that I discovered in the box adjacent to the labels.


 See a piece of equipment used for setting up receivers and transmitters in WWI aircraft


 WW1 Aircraft Transmitter HT Transformer

 This ancient wooden cased item is a transformer used in a WW1 transmitter, much like the one pictured above where you can see a similar transformer embedded in the outer box. Because a transformer needs to work on AC not DC, a springy steel strip is arranged to vibrate (like a buzzer). Battery current to the transformer's primary coil passes through a springy steel strip and iron-cored solenoid which pulls the springy strip so it no longer carries any current. The natural springiness of the strip then allows it to make contact again, thus allowing current to flow whereupon the whole cycle repeats. In this way an AC voltage is produced across the primary coil which is magnetically coupled to the secondary coil which carries a lot more turns of copper wire. A 6 volt battery can then produce several hundred volts of rough AC which is used to power the transmitter. In the example below the springy strip and the near contact are missing, however... hidden away in a tiny latched box in the unit above, I found a complete set of spares which would I could use to fix this example. see above.

I notice this version of the power supply has a hole under the free end of the spring steel strip. This was originally fitted with a second adjuster which, when combined with the main adjuster, could set the frequency of operation. This frequency, which may have been maybe several hundred cycles per second could be used to identify the particular transmitter. Most WW1 transmitters were of course spark transmitters and had a very broad output frequency and, if the waveband in use had a lot of transmissions, one could identify these from the pitch of their morse code. It seems aircraft transmissions used a higher frequency spark than trench transmitters to identify them as such.


Below you can see the end of the (rusty) iron core used for attracting the springy steel strip. The hole orinally carried a screw on which there were a combination of metal and rubber washers used for altering the natural resonant frequency of the spring steel strip (also missing). The inventor, Mortimer Arthur Codd was a motor engineer, born in 1880, who in 1911 was running a small business employing 20 men making parts for the electrical system of motor cars. During WW1 he branched out and was interested in power supplies for spark transmitters, hence the 1915 patent mentioned below the next picture. I looked for this chap in the 1911 census and found something of passing interest. He was included twice.. once by himself at 15 Dryden Chambers, Oxford Street (presumably his factory) and then by his father who registered his son at his own address of 20 Palace Road, Streatham. His father was clearly slightly unusual as he complained on the census form about having to question his deaf maid as to her birth details and was he fibbing about the exact whereabouts of his son? Dryden Chambers used to be an arcade at 119 Oxford Street, filmed in Hitchcock's film "Frenzy", but it's now built over by shops and the alleyway no longer exists. Is that perhaps where this little box was made?

  Below, I've turned the picture so you can read the numbers. I eventually discovered that the patent number was GB191514382 which was revealed to be a method of producing a higher than usual spark transmitter tone for use by aircraft.

Click to see the patent which was taken out by Mortimer Arthur Codd.


 Below are a couple of pictures of aircraft radios. The HT power supply above could have been fitted to either type. You can clearly see the adjuster for the buzzer and the battery wires connecting to the door. In the picture on the right you can see the black adjusting knob for the patented method of setting the pitch of the spark transmission. The springy steel part is a different shape to that in the trench transmitter, having a circular shaped section over the solenoid core. The right hand example is fitted with an aerial current meter and it's possible I have one of these (click to see it).

Example of a German WWI Field Telephone

 All the pictures below are photographs of equipment on display at the ImperialWar Museum (who have more resources than me) and alas are not in my collection

Thanks to Bob Norman for the photo.

All I've got is the wooden box behind the handset. If anyone's got any other bits for my collection I'd like to hear from them!

To see more of my box click the picture

Below is a phone being used, in a rather luxurious dug-out rather than a field!

Below is the British equivalent, A WWI Army Field Telephone

Unfortunately I don't have one of these, however I've now acquired a couple of other types since John Northmore kindly contacted me

Click to see pictures of these


 Intelligence activities based on the interception of military radio and telephone traffic proceeded apace. It would be many years though before the words "SIGINT" and "COMINT" would be coined, and intelligence to be assimilated and disseminated fast enough for it to make much difference. The first substantal organisation had Bletchley Park as HQ, then later it was GCHQ in Cheltenham (where I once used to work). Six key aspects are involved: identification of what to tune in to; interception and storage of information; decryption so it can be read; translation into English; analysis of usefulness and working out who might benefit; then dissemination to customers (which of course, nowadays, usually means re-encryption).

Alongside developments in communications, and advances in the speed of providing information to those who most needed it, were developments in coding and cryptography, aimed at slowing down or completely preventing the gaining of intelligence from intercepts.

This is an amplifier made by the same firm that designed the cryptographic equipment whose key was cracked by the Enigma computer at Bletchley Park some twenty odd years and a war later.

When a telephone was used to signal from a WWI trench an earth connection was usually made, and through the earth connection a signal flowed into the ground. The majority of the signal took the easiest path between sender and receiver but lots of current also passed by more roundabout routes. Because trenches rarely followed straight lines anyway, a good proportion of the earth current was detectable at nearby German trenches and if connections were made to ground at two widely separate points enough of the current was available to drive a sensitive detector. The amplifier shown used four triode valves and was able to amplify tiny intercepted earth currents sufficiently for an eavesdropper to listen in on enemy communications.

To see more military equipment, click the pictures below...

Old panelWWI phonesWWII phonesreturn to entrance