Siemens Fire Control Instruments

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Siemens manufactured a variety of direct working fire control instruments and bells for shipboard communication. The Royal Navy tested and deployed in 16-18 pre-dreadnoughts a variety of early instruments, but soon settled on the step-by-step instruments manufactured by Barr and Stroud and Vickers for installations after around 1907.


Prototype Design and Testing

Siemens "A" Equipment c1904[1]
Step-by-step ranges in 100s of yards.

In 1903, Siemens received permission to send a set of step-by-step transmitters and receivers to Vernon for testing and evaluation, claiming to have overcome difficulties then associated with such devices.[2]

In 1904, testing was done with 2 types of Siemens gear. "Siemens A" was a very reliable 4-wire step-by-step system (Vernon reported it had "never been known to miss a step") for conveying ranges or deflections. Vernon seemed well pleased with it, asking only that the range model be arranged in 25 yard step sizes rather than 100 as demonstrated, and that illumination at the receiver and a reply acknowledgement lamp back to the transmitter be stricken. "Siemens B" was a 10-order direct-working instrument pair employing a large number of wires between transmitter and receiver. That same year, this defect was offset by an innovation of Lieutenant C. R. Nicholl, who reduced the number of wires by using them to indicate in some binary fashion the position the transmitter means to send.[3]

Mark I Instruments

The Siemens Mark I family of instruments were early examples of direct working equipment. They did not spring out of the step-by-step initiatives of 1904 and probably preceded those trials.

The range of indications they permitted (maximum range 9975 yards) was to prove insufficient for tactical demands of the coming war. In 1909, 13 ships (Albion, Goliath, Ocean, Vengeance, Canopus, Royal Sovereign, Royal Oak, Empress of India, Resolution, Barfleur, Powerful, Terrible, Revenge) were listed as being equipped with Mark I.[4] By 1914, the only ships fitted with Siemens Mark I gear were the five of the six Canopus class ships: Albion, Goliath, Ocean, Vengeance, and Canopus.[5]

Siemens Range Transmitter Mark I[6]
Now able to send ranges in 25 yard increments — and by direct working.

The Pattern No. 90 Range Transmitter was apparently an old system, capable of sending ranges from 0 to 9,975 yards. It had 3 handles on it, each able to indicate a figure on a quadrant underneath. Inside, drums would rotate to establish the proper connections to energize wires needed to replicate the indicated figure on the receiver. Drums A and B had 10 positions (0-9) to convey thousands and hundreds of yards, and drum C having 4 positions to convey 00, 25, 50 or 75. Consequently, the reading could not be read across, but your eye would have to see which number was being pointed at in each of the 3 positions. The levers had a small push-button on their tips which presumably had to be depressed before the lever could be moved to another position, and which locked it precisely in one of the positions when released.

Siemens Range Receiver Mark I[7]

The corresponding Pattern No. 86 Range Receiver also had 3 drums to indicate the range, each with a star-like ring of electromagnets (10 in A and B, 4 in C). The 28 wires connecting the transmitter to the receiver would cause the 3 drums in the receiver to spin to indicate the range commanded at the transmitter, as it energized the proper electromagnet within the drum, causing it to spin to allow this particular magnet to face one on the housing. Presumably, the range was read off a line of windows permitting the labelled faces of the 3 drums to be read. I do not know if the housing was rectangular or had a rounded front face or top edge.

The Pattern No. 88 Deflection Transmitter and Pattern No. 84 Deflection Receiver were minor adaptations of the range instruments. The sole difference was that the rightmost (C) drums had "Right" and "Left" written on it rather than 00, 25, 50 or 75. I do not know whether there were 2 or 4 positions for the transmitter's rightmost lever. One would imagine they'd have tweaked it to have just 2 positions. By Royal Navy practice, then, the Mark I. deflection gear could indicate 99 knots left or right deflection as a maximum, which was an ample domain.

Siemens Order Transmitter Mark I[8]

The Pattern No. 89 Order Transmitter allowed the relay of firing orders by the position of a clock-like indicating hand. There were three positions it could assume -- the one at the 12 o'clock position was labeled "CEASE", the one at 4 o'clock was "CONTROL", and at 8 o'clock "INDEPENt" with the T curiously shrunk to connote the abbreviation of "independent".

Siemens Order Receiver Mark I[9]

The Pattern No. 85 Order Receiver had a small window through which "Control'd". "Cease" and "Independent" (from top to bottom) could be read on the swinging sector visible through it. Apparently, a loss of power at the device would cause "Cease" to be the setting indicated, as the other two positions are obtained by magnetic influence overpowering a centering spring device. The device needed 2 wires for its electromagnets (coming from its transmitter) and a single wire for its return.

Mark II Instruments

Siemens Mark II Instruments
Pattern 96 Range Transmitter
Pattern 83 Range Receiver
Pattern 94 Deflection Transmitter
Pattern 91 Deflection Receiver
Pattern 95 Order Transmitter
Pattern 92 Order Receiver
Pattern ?? Rate Transmitter
Pattern ?? Rate Receiver
Siemens Range and Deflection Instruments, Marks I and II[10]

The Mark II family of devices were refinements of upon Mark I and identical to them in general appearance.[11] They were installed in 5 (possibly 6... Centurion is omitted some sources) ships around 1906-1907.[12]

In 1909, Glory, Hood, Renown, Ramillies and Repulse were listed as having these;[13] By 1914, obsolescence of these vessels left only Glory equipped with these instruments.[14]

The drums in the Mark II instruments employed 5 magnets instead of the 10 used in Mark I, and this allowed fewer wires (15 + 2 power leads of larger diameter) to be used to tie transmitter to receiver. The full range of 10 indicating positions for the drums A and B was retained by clever combinations of electromagnets being employed rather than the use of a single magnet for each position as in the Mark I devices. It seems possible that this reduction in number of wires sprang from the suggestion made by Lieutenant Nicholl regarding the earlier Siemens "B" instrument.

There was also a Siemens Mark II Rate Transmitter and Receiver pair (no Pattern Nos. assigned, apparently) which bore close resemblance to the range instruments, but with an 4th element and handle. Drums A, B and C had 10 positions and communicated values from 0 to 99.9 in tenths. The fourth handle had 3 positions: "Open", "Close" and a blank spot showing when no rate should be taken from the indicator. It required the 17 wires of the Mark II range instruments plus an additional 2 wires for the fourth element. I presume the units were number of seconds for range to change 50 yards.

In 1909, instructions were offered to convert a proportion of Siemens Rate instruments for use as single range instruments.[15]

See Also


  1. Annual Report of the Torpedo School, 1904, Plate 39.
  2. Annual Report of the Torpedo School, 1903, p. 81.
  3. Annual Report of the Torpedo School, 1904, pp. 93-4.
  4. Handbook of Fire Control Instruments, 1909, p. 56.
  5. Handbook of Fire Control Instruments, 1914, p. 72.
  6. Handbook of Fire Control Instruments, 1914, Plate 2.
  7. Handbook of Fire Control Instruments, 1914, Plate 3.
  8. Handbook of Fire Control Instruments, 1914, Plate 4.
  9. Handbook of Fire Control Instruments, 1914, Plate 5.
  10. Handbook of Fire Control Instruments, 1914, Plate 1.
  11. Handbook of Fire Control Instruments, 1914, p. 13.
  12. All 6 listed in Annual Report of the Torpedo School, 1906, p. 82. and 'Paper prepared for the Director of Naval Ordnance and Torpedoes for the information of his Successor July 1907 and November 1909.
    Centurion omitted in Handbook of Fire Control Instruments 1909 and 1914.
  13. Centurion omitted from Handbook of Fire Control Instruments, 1909, p. 56.
  14. Handbook of Fire Control Instruments, 1914, p. 72.
  15. Handbook of Fire Control Instruments, 1909, p. 29.


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