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Courtesy of Barrie Smith and Pierhead Publications.

Synchronome Section

Frank Hope-Jones.

The Australian connection.

Early years of the Synchronome Company.

The Standard Master or 'A Frame' clock. Notes, dates, Variations etc.

The Double A Frame movement.

The Shortt-Synchronome Astronomical Regulator.

Other components of the Synchronome system.

Finding Set Up instructions.

Serial Numbers.

Frank Hope-Jones

Frank Hope-Jones
Frank Hope-Jones (1867-1950) was an outstanding figure in the horological world. He was a perfectionist, always seeking a better performance from the clocks he made and demanding an extremely high standard of finish both to the cases and the movements.

He had wide ranging is shown by this list of some of his many activities:

Chairman, Vice-President and Gold Medallist of the British Horological Institute;

Honorary Member of the Horological Institute of America;

Honorary Member of the Horological Society of New York;

First Fellow of the New Zealand Horological Institute;

Member of the Institution of Electrical Engineers;

Fellow of the Royal Astronomical Society;

First Chairman of the Wireless Society of London;

Chairman of the Radio Society of Great Britain;

Medallist, the Royal Society of Arts, London, the Institution of Electrical Engineers, London, and the Franklin Institute, Philadelphia.

The Horophonehorophone chartHis interest in radio, or wireless as it was at first called in the UK, tied in with his interest in horology, so by 1913 The Synchronome Company was manufacturing its ‘Horophone’ (Figure 2), a receiver with a crystal detector designed by Frank to bring in time signals, weather reports and news broadcast in Morse code from a few high powered wireless telegraphy stations such as that at the Eiffel Tower in Paris. The Horophone was built to the meticulous standards one would expect from a clock making firm.

This was very early days for radio and the signals had to be interpeted with the help of a graphic chart.

In 1923 Hope-Jones suggested to BBC engineers the idea of an automatic clock which would provide five pips as a time signal The idea was taken seriously and after the Astromer Royal (Frank Dyson) added an additional (and according to Hope-Jones, an unneccessary pip) it was adopted and the signal, produced by equipment designed by Hope-Jones, was first broadcast in 1924.

The Australian Connection

A G Jackson (1863-1935) did something quite unusual when in 1903 he purchased rights to the Synchronome name and patents in Australasia for the sum of £500. It is said that this purchase helped tide Synchronome through a difficult period.

Jackson incorporated his business under the name "Synchronome Electrical Company of Australasia" in 1904 and in the same year installed the first Synchronome electric tower clock in the South Brisbane Town Hall, Queensland. There was an interchange of information and ideas between Jackson and HJ and some letters from Jackson to HJ which have survived give glimpses of their relationship. sadly, no trace of HJ's replies have been found.

NAWCC published a booklet in 1998 under the title of "Synchronome Brisbane 1903-1991" which paints a comprehensive picture of the Jackson family and interesting material on the Web includes an article which appeared in the Horological Journal in 2006 under the title "The Synchronomes at the ends of the world"

Jackson mvmntThis picture shows one of the Australian early movements.

At the time Hope-Jones was still using a pendulum supported from the case backboard with a separate movement and it was Jackson who linked the pendulum support and the movement, an idea possibly later adopted by Hugh-Jones when designing his famous A Frame.

Other features of the Australian movements were that the pendulum was impulsed by a leader and crutch attached to the top support and also that the Australian movements made no provision for an advance/retard mechanism.

Early years of the Synchronome Company

In 1895, HJ who was then working with GBB (1875-1942), formed the Synchronome Company, took out their first patent and started production. The Company was initially based in Birkenhead.

click to enlargeHJ spent some thirteen years developing his 'sync switch' as he termed it.

click to enlargeSecond page. These two extracts from an early Synchronome catalogue sets out clearly how this switch worked and gives his views on why his system was the best (and in his view, the only, way forward).

In the first few years the clocks were of differing styles and movements and had no serial numbers.

click to enlargeThe first clocks had a recoil or a dead beat escapement. Clear pictures of these early clocks are hard to find and by far the best I have came from Norman Heckenburg and shows a 1904 English built electrically rewound spring driven deadbeat escapement used to control the Town Hall clock in South Brisbane, Australia. see 'The Australian connection'.

Norman is Reader in Physics at the University of Queensland and director of the Physics Museum there. He was a member of the NAWCC Chapter 104 team which produced the booklet 'Synchronome Brisbane 1903-1991' in 1998.

The most radical change was in 1905 when the dead beat escapement was superceded by a gravity escapement. British Patent 6066/1905 describes a gravity arm tripped by a countwheel which impulses the pendulum directly once every thirty seconds. The countwheel was pushed around anticlockwise and it was not until later that the usual syatem of pulling the countwheel clockwise was evolved.

click to enlargeI include a blurred picture of an English movements from this early period, but this shows no detail though the gravity arm can be seen.It should be noted that the movement has a rectangular brass base, not the cast iron A frame of later clocks.

The final patent for his Master Clock design was granted in 1908. By that time the partnership with GBB had been dissolved and the company was based in London.

The Movements

The "A" frame movement

Serial C 103

In 1908 the company produced the now famous "A" frame movement and from that time on all genuine Synchronome clocks were given a serial number.

There were some minor variations in the movement of early models, for example early clocks had slightly different arrangements of the latch for the gravity arm and had no buffer to limit the travel of the gravity arm.

Useful date clues:

After 1926 a buffer was fitted to all "A" frame movements.

Up to circa 1930, the A frame was a fairly roughly finished casting and was painted with a black paint, often quite dull, almost matt, in appearance. Later clocks have a better finish to the casting and black crackle finish.

In the spark suppression circuit, wire wound resistors were used up to the 30's and carbon resistors thereafter.(These resistors are hidden behind the "A" frame)

The coil of the electromagnet which resets the gravity arm was wound with green coloured silk insulated wire in early clocks. Later clocks have a winding of enamelled wire finished with a wrapping of a black material. One source suggested that the changeover was circa 1934 but my records show at least some green wound coils up to 1950. No doubt there was a period when coils of both types would have been in stock.

The Mark II movement

Serial 5483

The Mark II movement was introduced around 1962. It strongly resembled the earlier "A" frame movement but had been modified for ease of manufacture with most parts now assembled from stamped brass held together by nuts, bolts and spacers.

A separate series of serial numbers was used for clocks with the new movement.

Shortly after the movement was introduced, around 1965-70, a new broad case was introduced for the Mark II movement in which the movement was offset from the centreline of the case and the glass in the cases was often painted black.

Synchronome supplied castings and parts

Made from Synchronome parts

During the 1930s and early 40s the company made castings and parts for the Synchronome "A" frame movement available to enthusiasts.

Clocks built from such kits or parts are often found and are frequently finished to a high standard.

They can be distinguished from a factory built Synchronome because they have no serial number on the NRA plate.

Some clocks built from castings and parts supplied by Synchronome do not have the NRA feature.

Case Styles

I have named and numbered the case styles for my own convenience.
I do not suggest that Synchronome used any such names or numbers.

Very Early Clocks

Early with pedimentA very early model with pronounced pediment and well shaped bracket base

See later for some information about early movements.


Style 1 The Architectural style

Serial 438Synchronome started to use the Architectural style of pediment (a rooftop appearance) in 1900.

At that time they were producing an early form of movement.

Note the carved detail in the top corners of the door. The door is inset into the case, not overlapping the front as in later clocks and though not visible in the picture the bottom of the case is finished as a well shaped bracket.

In 1908 the countwheel escapement came into production using the typical A shaped backplate. the use of serial numbers commenced from the introduction of this model, probably starting from "1" since the remains of clock serial 15 are known.

At this time both the earlier designs and this new A Frame model were offered in cases of Walnut, Mahogany or Oak.

The walnut and mahogany were of the highest quality and impeccably polished. By the nature of the wood, Oak does not accept such a high polish but the quality was of the highest order.

The finish on the movement was reminiscent of that used for scientific instruments, rather than the usual 'clock' finish.

The architectural style case continued in use until circa 1919.


Style 2 The False Pediment style

Serial 1904

In 1919 the false pediment is found, that is a flat top with a triangle shape mounted on top of the case so that from the front it resembles the architectural style.

The picture shows one of the earliest of the false pediment models with elaborate mouldings to the projecting top and bottom portions of the case and the door inset into the case.

There may well be slightly later models with simplified mouldings, though I understand that Synchronome did not themselves manufacture the cases (or some of the movements?) so the differing types of false pediment may just be variations introduced by subcontractors.

Clearer view of false pediment

I have been told that the use of a false pediment ceased circa 1922 (serial 954 is known to have a false pediment) and it is possible that the false pediment style is the least common type of case.


Style 3 The Flat Top style

serial 2119

From 1922 to 1948 a flat top style was adopted.

The top and bottom of the cases project and are finished with a shaped moulding.

There are several variations with slightly different mouldings and/or different door latches. Some of these variations are shown in the "Basic design changes" section below.

Serial 1088Synchronome bought ex WW1 16 lb shells and supplied these as pendulum bobs for several clocks at this period.


Style 4 The "Round Corner" style


After the war, in about 1948, a case with rounded corners was introduced.

All the cases in my records have either a piano finish black case with chrome fittings
or an oak case and brass fittings. This applies also to the type 4A cases.

This continued in use until the new broadcase for the Mark II movements was developed.


Style 4A The "Round Corner" style with bar below dial


This is a sub-style of type 4, the standard "round corner" model.

I believe it occurs near the end of the series.

As you can see it has a square dial and a bar across the door below the dial.

When the mark II movement was introduced it was at first fitted in this type of case
but within a year or two a new case, the (type 6) Broad case style was introduced.


Style 4B


This is another variant of the type 4 case.

The top of the case extends over the door.


Style 5 Metal Case.

Power Station

This model was used in Power Stations.

There are also some models having an all metal case, that is, no glass in the door.

These latter were made for The London Underground.


Style 6 The Broad Case style

serial 705This was a wider case in a plain style with the movement offset from the centre line.

It was introduced circa 1964

Here again there are several minor differences in style. Clocks with no pilot dial are known and the clocks may have plain or black painted glass to the door.

Note: Mark II movements introduced in 1962 were initially fitted in a round corner case (style 4A).


How the basic design changed over the years

As the Synchronome movement was in use for over 70 years it is not surprising that there were changes, what is perhaps surprising is that there were so few alterations.

The most noticeable change was the introduction of the Mark II movement in 1962, but even this unfortunate abandonment of style for utilitarianism had little effect on the movement itself. It was followed by the introduction of a new broader case circa 1964. Throughout the life of the Synchronome minor changes were made, both in case styling and in the movement, and a few of these are detailed below.

I understand that prior to 1908 some of the very early clocks were built in such a way that the wheel was pushed, rather than pulled by the swing of the pendulum, but that this was quite quickly abandoned in favour of the system as we know it with the wheel pulling a tooth forward by the swing of the pendulum.

Latch Holding Gravity Arm

Several different methods were used in the early clocks to hold up the gravity arm until the correct moment for its release to deliver an impulse to the pendulum. One of these latch systems had a leather lined V notch which prevented overtravel of the gravity lever when it was restored by the electromagnet.

I have not been able to find any evidence of the dates of these latches.

View pictures of some of these latches.

Adjustable Buffer

The bufferThe final form of the gravity arm latch included an adjustable buffer
fixed to the backplate and this was introduced in 1926.

The highest serial number I have yet heard of with no buffer is 1224

Changes to "A" frame, spark suppression and coils

A noticeable change is that from 1930 the "A" frame itself was smoothed off and finished in crackle enamel. Previously the frame had been a fairly roughly finished casting which was painted with a black paint, often quite dull in appearance.

The coil of the electromagnet which resets the gravity arm was wound with green coloured silk insulated wire in early clocks. Later clocks have a winding of enamel insulated wire finished with a wrapping of a black material. The changeover was somewhere between 1934 and 1950. The pictures I have at present show both black and green coils in that period. (Some may be service replacements or rewinds).

In the spark suppression circuit which is beneath the "A" frame, wire wound resistors were used up to the 30's and carbon resistors thereafter.

Pictures of more Synchronome movements are needed to narrow those limits.

Case Locks and Latches

Variations in case locks and latches can be noted but further investigation is needed before this helps with dating.

Up to the present, I know of two types of locks and eight types of latch:

1. Single lock Single lockThis was a single lock with the keyhole in the front of the case, no latches.

2. Two locks

lockThe locks are fitted in the sides of the case.Two keyhole escutcheons in the side of the case are all that show externally. No latch.

3. Old style turn latch

serials 954, 19044. Turn latch with "T" shaped handle, fitted to the front of the case (which has an inset door) The keep of the latch turns into a cast brass catch fitted to the edge of the case side. Two latches fitted to each case, no information about a lock.


serials 405, 4085. Another turn latch with "T" shaped handle, fitted to the front of the case.

No information about a lock.

serials turn latch6. Turn latch with "T" shaped handle, similar to No.5 above, fitted to the front of the case.

No information about a lock.

7. Latch with clamping action.

serial 734The clamping lever is fitted to the front of the door, with the keep plate on the side of the case. A turnbuckle on the side plate is a further safeguard against accidental opening

8. Another Latch with clamping action.

serials 1167, 1389This has the clamping lever on the side of the case.

9. The most common latch

common latchHook and pin type latch. The "hook" is a swiveling arm fitted to the edge of the door which rotates into a pin fitment on the side of the case. Two such latches and one centrally placed lock are fitted to each case. This type was used for the vast majority of clock cases produced by Synchronome.

10. Clipover latch

used on MkII modelsThis form of fastener was probably only used on a broad case (style 6). It is a latch similar to that used on brief cases etc.. The latch covers all screws when closed and tightens the door against the felt insert usually fitted to the case edges. Two latches are fitted to each case. Lock also normally fitted.


Mouldings to top and bottom of type 3 clocks

Shown below are four of the many styles used.

I believe these mouldings were left to the discretion of the various subcontractors who supplied the cases.

Additional Mechanisms fitted in some clocks

Seconds indication

Serial 2991Main dial shows seconds, 
small inset shows hours and minutes 

Serial 2991The additional unit to provide seconds pulses 

Serial 1162A Mark II movement
with added seconds unit 

Serial 2429

Synchronome 2429 with twin dials 

Additional units, purpose unknown

Serial B75 space Serial 966
Unit mounted top of "A" Frame, Has mercury switch space Hit & miss synchroniser mounted
on backboard below "A" Frame

Serial 969 space Serial 1296
Unit below "A" frame. has slaved ratchet wheel

space Unit with "flag" indicator
Serial 5289 space Serial 5335
Synchroniser? space Mercury switch unit well below "A" frame

Slave movements for driving the pilot dials

Many pilot movements show a serial number which differs from the main movement.

Synchronome bought in many of the pilot movements and makers probably applied their own serials.

Serial 1841 Serial 5527
Pilot movement most often seen Similar with wire wound shunt resistor

Serial 2991 Serial 3179
Movements for separate seconds dial Similar movement

Serial 4585 Serial 4807
Pilot movement of different design Replacement movement, probably Gents, in serial 4807

Serial C 185 Serial 315
Smaller type of pilot movement Pilot with extra cam and contacts
serial 1730 space Serial 2390
Serial 4024 space Serial FP340

The Double A Frame Movement

Around 1920 (1922 according to Rita Shenton in "Collectable clocks"or 1919 from other sources), The Synchronome Company introduced a new model, now often called the "Double A Frame" or AA frame clock which had been patented during the 1914-18 war. It was found that it did not provide any great improvement in accuracy and needed expert technical skill to set up and maintain so it only remained in production for one year and only about 150 clocks were produced.

It is nevertheless a very desirable collectors item and I am honoured to have received a set of photographs for the museum.

AA Synchronome
click to enlarge click to enlarge click to enlarge click to enlarge click to enlarge

Other Components of the Synchronome System

Slave Dials or Secondary Dials

These are found in huge numbers as most Synchronomes were used to distribute the time they indicated to many slaves spread round the factory or offices in which they were installed. Only a few samples are shown here.

Wall dials and a rare Mantel or Boardroom clock.

click to enlargeclick to enlargeclick to enlarge

External dials for turrets, churches or Offices.

click to enlargeclick to enlarge

Programme controllers

Controllers were used for operating electric bells, hooters, syrens and all other forms of warning signals, to a predetermined programme in exact synchronisation with the clocks in the premises.

click to enlargeThe program Controller widely used

This controller usually has a built in Duration Reducer limiting the sounding of bells etc. to approximately 10-12 seconds as 30 seconds was often found to be too long. An Automatic Week-end Silencer can also be provided and a mercury tube contact to carry 5 mps at 230-250 volts is a standard fitment.

click to enlargeAn Automatic Bell Controller from an earlier catalogue.

click to enlargeAn Automatic Time Switch (also from an early catalogue). The function is to control secondary circuits such as the lighting of public bracket clocks etc. at pre-arranged times. The contacts are substantial and intended to handle currents at up to 250 volts.

Marine Installations

click to enlargeClick on the picture 
for the full descriptive page 
from a Synchronomr catalogue.

Trickle Chargers

click to enlargeclick to enlarge

Synchronome setup

I had intended to give full setup details here, but as there is so much information already available on the Internet it seems more sensible to mention the two points that I think give the most trouble to those attempting a setup for the first time

Firstly, It is ESSENTIAL that the clock case is firmly fixed to a wall and the case must be set absolutely vertical, both front to back and side to side.

Most clock instructions say this but it is usually disregarded on the grounds that "this is only a test"!

The Synchronome was designed to allow the pendulum to swing as freely as possible and the gravity lever if properly set, provides only just sufficient energy to keep it swinging. If the case is not fixed then the heavy pendulum will cause tiny movements of the case and these use energy required to keep the pendulum swinging.

click to enlargeSecondly, the setting of the gathering arm with its jewel is vital. It might seem logical for it to be set so that it fully engages the countwheel while it pulls that wheel forward but it was not designed that way and causes far too much load on the pendulum, which as I have said, was intended to swing as freely as possible.

The gathering arm should be set so that it only engages a tooth of the wheel just barely sufficiently to pull it forward one click. This is mentioned in all the instruction I have seen, but it is not sufficiently emphasised.

Where to find full instructions

When this was written, November 2009, the following web sites are worth looking at: Look for the Synchronome section and within that the adjustment notes. This has a copy of the notes by A Mitchell which are widely recommended.

Serial Numbers

Starting around 1908, when the "A" frame model was introduced, the Synchronome Company marked all production of this type of clock with a serial number (perhaps with one or two early exceptions) and as there was a clock with the number "15" it is assumed that the first number in the series was "1".

It is unfortunate for collectors that they did not date individual clocks, nor is any cross reference list known which would accurately correlate a serial number and the date of manufacture.

In a very few cases there is external evidence of the date of supply, such as an original invoice, so it is possible to interpolate and so obtain an approximate date from a serial number. Information on accurately dated clocks is so rare, however, that the interpolated data can also vary quite a bit and much depends on the assumptions made by the interpolator!

Serial Numbers in detail

The first clocks produced by the Synchronome Company were of differing styles styles and movements and had no serial numbers.

Serial numbers were introduced cira 1908 when the now famous "A" frame design was introduced, and from that time on (perhaps with one or two early exceptions) all genuine synchronomes were given a serial number.

The serial number was stamped on the Advance /Retard plate (commonly refered to as the NRA plate) which is fitted at the left side of the "A"frame. A few early clocks had the serial on a Synchronome label.

A very few Synchronomes had the number on the armature bridge (Always in cases where no NRA plate is fitted such as when used with a synchroniser).

Numbering is thought to have started from "1" because the remains of of clock serial "15" are known.

During the life of the company, ie up to around 1982, several different series of numbers were used, but two series were predominant.

First Series

The first series ran from 1908, when Synchronome started to put serial numbers on their clocks, until about 1962. I do not know the highest number reached, but 6134 is thought to be one of the highest.

Second Series

When the Mark II movement was introduced in 1962 a new range of serial numbers was started for this movement.

This series probably started from "1" as serial B15 is known.

The highest number I have heard of is 5850.

The first mark II movements were fitted in style 4A cases (round corner cases with bar under dial) as the new broad case (style 6) was not introduced until circa 1964.

Coventry Series

This is a separate series which uses the letter 'C ' in addition to a number.The probable dates for such clocks are between 1928 and 1939.

These clocks are believed to have been made for Synchronome by a maker in Coventry, and the Letter"C" may precede the number or be above it.

Occasionally another letter is used with a number. For example, I have a picture of a clock with the NRA plate marked FP 340.

The Shortt-Synchronome Astronomical Regulator

Frank Hope-JonesWilliam Hamilton Shortt, an engineer on the London & South Western Railway, became interested in precision timekeeping in 1906 and patented his own clock in 1911. The early examples did not reach the standard he had set himself and he continued to work on the project. He had met HJ in 1910 and at some time before 1921 he became a director of the Synchronome Company. 
The Shortt Free Pendulum Clock was patented (Patent No. 187814) in 1921.

It was manufactured by the Synchronome Company and used a virtually unmodified standard Synchronome clock as the slave clock in the system. It became the standard timepiece for observatories all over the world until superceded, years later, by the precision quartz crystal clock.

A good and fairly simple description of the Shortt-Synchronome can be found in Britten's Watch & Clockmaker's Handbook and Guide 16th edition and rather surprisingly, a more detailed account is given in Eric Bruton's book on the History of Clocks and Watches.

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