The receiving apparatus used during the successful 1858 transatlantic cable operation was a sensitive mirror galvanometer. This device detected minute changes in the electrical current transmitted through the cable. These fluctuations caused a delicate needle, which was attached to a mirror, to shift and reflect a beam of light onto a screen. An operator read the light patterns caused by these movements and relayed the information to a second operator, who then manually transcribed the signals.

In 1864, George B. Prescott detailed an improved version of this system in his book *History, Theory, and Practice of the Electric Telegraph*. Prescott described a setup where the operator observed the needle’s movements reflected in a mirror. A key, connected to a local recording instrument, was used to mark the needle's deflections. One operator handled the key, pressing it up or down to match the needle's movements, while another deciphered the characters recorded on paper. Despite these advancements, the system was limited to a maximum speed of three words per minute over the cable.

This early method was eventually superseded by the Siphon Recorder. Unlike its predecessors, the Siphon Recorder printed incoming signals directly onto tape. This system employed a dual-lever 'cable key', distinct from the simpler railway tapper key previously used. Pressing the left lever sent a positive signal (a dot), while the right lever sent a negative signal (a dash). The tape displayed these signals as Morse code, with dots and dashes represented by undulating lines. Unlike the tapping method used on landlines, the key was gently pressed to accommodate the slower transmission speed of the cable. In the recorded output, dots appeared as deflections above the line and dashes as deflections below. Some characters were recognizable to an untrained eye, but others required skilled interpretation by an experienced operator.

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Morse in the armed forces

Until World War I, the British Army and Navy employed similar Morse code signaling techniques, albeit with some variations. During the Crimean War (1853-1856), the Army utilized both sounder and single-needle telegraphs. These devices transmitted Morse code over cables laid on the ground, or when conditions allowed, suspended overhead or placed in trenches, as depicted in Figs. 3 and 4. For instance, in the rugged terrain of Crimea, the Army adapted their setup based on the geographical challenges, such as using trenching for stability and protection.

With the advent of the 20th century, significant advancements were made in military communications. For the first time, during the South African War (1879-1880), British forces were able to communicate directly with the War Office in London through telegraphic traffic routed via civilian landlines across Europe and newly established cross-channel submarine cables. This was a major leap from the earlier reliance on slower, less reliable methods.

During this period, the telephone, a relatively recent invention, was experimented with in the hope of improving communication reliability. The goal was to receive Morse signals more clearly over poor-quality lines, which often plagued sounder operations. This experimentation led to the development of the 'vibrating sounder,' an innovative Morse buzzer signaling instrument. Invented in 1881 by Lieutenant Philip Cardew of the Royal Engineers at the School of Military Engineering in Chatham, this device was designed specifically to address the limitations of existing Morse equipment.

The effectiveness of the vibrating sounder was noted by Preece and Sivewright in their 1905 edition of *Telegraphy*. They highlighted its success in situations where other instruments failed due to weak signals caused by insulation faults on the lines. As they observed, "where other instruments fail from weak signals through faults of insulation on the lines, the vibrating sounder has proved eminently successful," underscoring its critical role in enhancing military communications during that era.

Disadvantages

The 1908 edition of Instruction in Army Telegraphy and Telephony, Vol. 1, also described the advantages of the vibrator system. It stated that the telephone receiver was very sensitive, and only a very small current was required; the circuit could be divided into two parts, enabling ordinary (ie, sounder) Morse currents to pass through one path, and the vibrating currents through the other at the same time.

Its disadvantages were that the vibrating currents induced similar currents in all neighbour-ing wires, producing buzzes in any telephone receiver connected to them, so that several vibrator circuits could not be worked by side for any dis-tance. It was more tiring to operate than ordinary sounder circuits; and the operating speed was slower.

The greatest problem came to light in the trenches in WW1, when it was realised that induction or earth leakage from the vibrating signals were being intercepted and read by the enemy. The problem was overcome by the Fullerphone, invented by Capt. A C Fuller, RE, in 1915.

Buzzers notwidelyadopted

Morse enthusiasts today, familiar with tone reception of Morse code, may wonder why landline telegraphy continued to receive code by

'clicks' and other sounds, and did not convert to tone signalling when suitable systems became available. The simple answer seems to be that the existing instruments provided long-established reliable communication, and it was generally believed that reading tone signals was more difficult than reading sounder or other signals.

Change would also have involved large-scale re-training of staff and the expensive installation of new equipment at a time when, faced with faster alternative systems such as the tel-eprinter, and ever expanding and improving wireless services, the writing was already on the wall for landline Morse. The vibrating sounder if it

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The 1908 edition of *Instruction in Army Telegraphy and Telephony*, Vol. 1, highlighted the advantages of the vibrator system. It noted that the telephone receiver was exceptionally sensitive and required only a minimal current to operate. This allowed for the circuit to be divided into two separate paths: one for standard Morse code currents and the other for vibrating currents. For instance, while one circuit could handle the continuous flow of Morse code signals, the other could manage the intermittent vibrations without interference.

However, the vibrator system had notable drawbacks. One major issue was that the vibrating currents would induce similar currents in adjacent wires, leading to unwanted noise or 'buzzes' in any connected telephone receivers. This interference meant that multiple vibrator circuits could not be operated in close proximity. Additionally, the system was more laborious to operate compared to the traditional sounder circuits, and it had a slower operating speed.

The most significant problem emerged during World War I, when it became evident that the vibrating signals could be intercepted and read by enemy forces through induction or earth leakage. This vulnerability led to the development of the Fullerphone by Captain A.C. Fuller, Royal Engineers, in 1915, which addressed these security concerns.

Despite technological advancements, buzzers remained in use for landline telegraphy. Enthusiasts of Morse code might question why tone signaling, which was available, wasn't adopted more broadly. The answer lies in the reliability of existing instruments, which had a long history of effective communication. Additionally, tone signals were perceived as more challenging to interpret compared to traditional 'clicks' and sounds. Transitioning to tone signaling would have required extensive retraining and the costly installation of new equipment. At a time when faster systems like the teleprinter and improving wireless technology were emerging, the future of landline Morse seemed uncertain. Although the vibrator system offered a glimpse of potential improvements, it did not achieve widespread adoption. However, the Fullerphone proved to be a valuable tool and was extensively used by the Army throughout World War II.

The heliostat and the heliograph were both pivotal in the evolution of optical communication technology.

The heliostat, first adopted by the British Army in 1875, was a device designed to reflect sunlight towards a distant station. It achieved this by using a shutter mechanism to transmit Morse code signals. For instance, during its early use, soldiers at various outposts employed heliostats to communicate critical messages across challenging terrains, such as the rugged landscapes of colonial Africa. However, this method had limitations in range and reliability.

An advancement came with the heliograph, which is depicted in Figure 6. Unlike the heliostat, the heliograph utilized an oscillating mirror to send Morse code, offering significant improvements in communication. For example, a heliograph with a five-inch mirror could effectively signal over distances of 50 to 70 miles under optimal weather conditions. This technology was particularly valuable in expansive desert regions where other forms of communication were less practical. Operation of the heliograph required a team of at least three people: one to call out or record the messages, another to maneuver the heliograph to send the signals, and a third to use a telescope to read and transcribe the incoming messages from the distant station.

The speed of communication with the heliograph could reach up to 12 words per minute, depending on the operator's expertise and weather conditions. The heliograph’s final documented use by the British Army occurred during the siege of Sollum Hayata in the 1941 desert campaign of the Eighth Army. This last operational deployment underscored the heliograph’s significance in wartime communication before being superseded by more modern technologies.

Navy Landlines

It might seem unusual that the Navy required its signalmen to master sounders and buzzers, which were primarily land-based signaling systems. However, this was a critical part of naval communication. For example, every large naval vessel was equipped with a Morse key for transmitting coded messages, a sounder for visual signaling, and a Post Office (P.O.) relay system to manage communications. Additionally, ships carried two types of cables: 1,000 yards of cable specifically for submarine use and another 1,000 yards for connecting to shore-based communication networks like the Admiralty or P.O. landline systems when docked. Depot ships, which were permanently moored, had significantly more—10,000 yards of cable for both submarine and shore-based communications.

Ships followed P.O. operating procedures and each vessel was assigned a two or three-letter Call Signal, which was usually an abbreviated form of the ship's name. For instance, HMS Victory might have a Call Signal of "HV" or "VY". To achieve effective communication, the Navy also employed two P.O. telegraph relays equipped with telephone receivers. These relays could be adjusted to vibrate, mimicking the performance of the Army's vibrating sounders when the sending key was pressed.

In terms of proficiency, naval signalmen were required to meet specific sending speed standards during their qualifying exams. For example, a Boy or Ordinary Signalman needed to demonstrate a sending speed of 12 words per minute (wpm) using a sounder or buzzer over a five-minute period. In contrast, a Chief Yeoman of Signals was expected to achieve a speed of 21 wpm. These speed requirements were comparable to those for army signallers of similar ranks.

Signal Lamps

The Navy first introduced flashing lamps for communication in 1867, but Morse code wasn't implemented until approximately 1874. These signal lamps evolved into two primary types: mechanically controlled and electrically controlled. 

Mechanically controlled lamps used a hand-operated disc or shutter to interrupt the light source, generating Morse code signals. For example, early signal lamps featured a rotating disc that blocked and unblocked the light from a candle or an oil lamp. Electrically controlled lamps, on the other hand, utilized a Morse key to create and break an electrical circuit, thus controlling the light output.

Initially, the light sources included candles, which were later replaced by burners and wicks using mineral sperm oil. As technology progressed, acetylene lamps and electric arcs became standard. The most advanced of these were electric arc lamps, capable of producing up to 2,000 candlepower. In ideal atmospheric conditions, these could be seen on the horizon by the naked eye, making them suitable for long-range signaling.

For closer ship-to-ship communication, more modest lamps were employed. Yardarm blinkers, which used a Morse key to send non-directional signals, were commonly used. These blinkers were simpler and ideal for short distances.

The army also utilized a variety of signal lamps, which could be handheld, mounted on spikes, or housed in portable cases. These lamps operated at speeds of 8-12 words per minute and could communicate over distances of up to four miles in the field. For extended-range communication, the heliograph was employed, using sunlight reflected via mirrors to transmit signals over greater distances.

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Flags

Morse signaling flags were essential tools used by both the army and navy for communication. These flags were designed with specific color schemes: white with a blue horizontal stripe was employed for signaling against dark backgrounds, while dark blue flags were used for signaling against lighter backgrounds.

To transmit Morse code, a single flag mounted on a staff was waved above the signaller's head. For instance, in the position illustrated in Fig. 7, the 'at rest' stance is depicted as position 'A'. To signal a dot, the flag was raised to position 'B' and then returned to position 'A'. Conversely, signaling a dash involved moving the flag to position 'C' and then bringing it back to 'A'. 

The proficiency requirement for naval signalmen, including both flag waving and flashing lights, was a transmission speed of 12 words per minute (wpm). This standard was equally applicable to army signallers. The effective signaling range of these flags extended up to four miles, demonstrating their utility in long-distance communication scenarios.

In the context of naval communication, two notable signaling methods were shutters and collapsing drums. 

Shutters, depicted in Fig. 8, were employed at permanent coastal stations to transmit messages to nearby ships. These devices consisted of a series of interlinked panels, each mounted on a pivot, which could be moved simultaneously using a central handle. When the shutters were positioned horizontally, they were nearly invisible to distant observers. In contrast, when oriented vertically, they created the illusion of a substantial object, allowing for the transmission of coded messages through the display of dots and dashes. For optimal visibility, the shutters were painted white with a black frame when used against a dark backdrop, and black with a white frame when set against a lighter sky or background. Their size could vary based on the required signaling distance; the largest recorded example had a surface area of 72 square feet and could be seen from 10 to 15 miles away under clear conditions, as documented in the Admiralty Manual of Signalling.

The collapsing drum, another key naval signaling tool, was designed primarily for communication between ships and shore stations. Typically erected 15 to 20 feet above the deck or ground, this device could collapse and expand manually. Its omnidirectional capability allowed it to send signals in any direction. As shown in Fig. 9, the drum, when extended by a line (marked C), displayed a light, whereas when collapsed, it obstructed the light, thereby enabling Morse code transmissions similar to those sent with a signaling lamp.

By the late 19th century, Morse telegraphy had become a global phenomenon, with its use spanning virtually every corner of the world. This widespread adoption created a consistent need for skilled telegraphists who could proficiently learn and utilize the Morse code. The demand for such professionals was met through various avenues: industry-sponsored training programs, commercial training schools offering structured courses and certifications, and an array of instructional books dedicated to mastering Morse code and excelling in telegraphy.

For instance, in the United States, the rise of amateur telegraphy mirrored the enthusiasm seen in later years for wireless telegraphy. Many hobbyists were driven by a dual interest: some sought to acquire Morse code skills as a gateway to employment within the telegraphy sector, while others simply enjoyed the novelty of setting up their own telegraph lines to connect with friends across town, purely for the pleasure of communication.

A notable example from this era is the 1884 publication by J.H. Bunnel & Co. of New York, titled "Students' Manual." This 48-page guide was designed to assist aspiring telegraphers in embarking on a successful career. Though it focused exclusively on American Morse code, the manual offers a fascinating glimpse into the learning and practice of Morse telegraphy over a century ago. It covered practical aspects such as constructing telegraph lines, ensuring proper earth connections, setting up two-way and multi-instrument circuits, and operating the battery. Additionally, the manual included procedures, common abbreviations, and other essential tips, providing a comprehensive resource for those entering the field.

The advent of wireless technology heralded the gradual decline of landline Morse telegraphy, though the transition was far from immediate. For instance, in Britain, the American sounder, a key device for receiving P.O. telegrams, continued to be used until the early 1930s. During this period, the Post Office began replacing the Morse telegraph system with teleprinters, marking a shift towards more modern communication methods.

The military, heavily reliant on sounders, faced the challenge of potentially losing skilled telegraphers trained in Morse code. To mitigate this, the Army opted to adopt the Fullerphone more extensively, an alternative technology that could better serve their needs. In North America, sounders remained in use until around the 1960s, and the final commercial Morse telegram sent via sounder in Australia was dispatched in 1963.

In Britain, the needle telegraph and double plate sounder, which utilized Morse code, were still in operation on railways until the 1970s. The Post Office's last inland Morse circuit, which connected the Outer Hebrides islands through a submarine cable, was discontinued in 1954 due to a fault in the cable, effectively ending this form of communication.

Today, beautifully crafted brass and polished wood telegraph instruments from the Victorian era are preserved in museums, heritage railways, and private collections. These artifacts stand as poignant reminders of a bygone era and a different technology, highlighting the once-significant role of Morse telegraphy in communication history.