Navigation menu



This is a five pole Sallen-Key low pass filter. if all the poles are in the correct position the roll-off rate is 30dB/octave. On casual inspection the second stage is a 2-pole Butterworth filter the . Used Rarely. roll off is in the lower 50% of commonly used words in the Collins dictionary View usage for: All Years Last 10 years Last 50 years Last years Last years Nearby words of 'roll off'.

Roll-off is the steepness of a transmission function with frequency, particularly in electrical network analysis, and most especially in connection with filter circuits in .

RORO vessels have either built-in or shore-based ramps that allow the cargo to be efficiently rolled on and off the vessel when in port.

While smaller ferries that operate across rivers and other short distances often have built-in ramps, the term RORO is generally reserved for large oceangoing vessels. The ramps and doors may be located in stern , bow or sides, or any combination thereof.

At first, wheeled vehicles carried as cargo on oceangoing ships were treated like any other cargo. Automobiles had their fuel tanks emptied and their batteries disconnected before being hoisted into the ship's hold, where they were chocked and secured. This process was tedious and difficult, and vehicles were subject to damage and could not be used for routine travel. The first modern train ferry was Leviathan , built in As bridge technology was not yet capable enough to provide adequate support for the crossing over the Firth of Forth , which was roughly five miles across, a different solution had to be found, primarily for the transport of goods, where efficiency was key.

Custom-built ferries were to be built, with railway lines and matching harbour facilities at both ends to allow the rolling stock to easily drive on and off the boat. The wagons were loaded on and off with the use of stationary steam engines. Although others had had similar ideas, it was Bouch who first put them into effect, and did so with an attention to detail such as design of the ferry slip which led a subsequent President of the Institution of Civil Engineers [3] to settle any dispute over priority of invention with the observation that "there was little merit in a simple conception of this kind, compared with a work practically carried out in all its details, and brought to perfection.

The company was persuaded to install this train ferry service for the transportation of goods wagons across the Firth of Forth from Burntisland in Fife to Granton. The ferry itself was built by Thomas Grainger , a partner of the firm Grainger and Miller. The service commenced on 3 February Train-ferry services were used extensively during World War I. From 10 February , high volumes of railway rolling stock, artillery and supplies for the Front were shipped to France from the "secret port" of Richborough , near Sandwich on the South Coast of England.

This involved three train-ferries to be built, each with four sets of railway line on the main deck to allow for up to 54 railway wagons to be shunted directly on and off the ferry. These train-ferries could also be used to transport motor vehicles along with railway rolling stock.

Later that month a second train-ferry was established from the Port of Southampton on the South East Coast. In the first month of operations at Richborough , 5, tons were transported across the Channel, by the end of it was nearly , tons. There were many advantages of the use of train-ferries over conventional shipping in World War I. It was much easier to move the large, heavy artillery and tanks that this kind of modern warfare required using train-ferries as opposed to repeated loading and unloading of cargo.

By manufacturers loading tanks, guns and other heavy items for shipping to the front directly on to railway wagons, which could be shunted on to a train-ferry in England and then shunted directly on to the French Railway Network, with direct connections to the Front Lines, many man hours of unnecessary labour were avoided. An analysis done at the time found that to transport 1, tons of war material from the point of manufacture to the front by conventional means involved the use of 1, labourers, whereas when using train-ferries that number decreased to around labourers.

This was of utmost importance, as by , the British Railway companies were experiencing a severe shortage of labour with hundreds of thousands of skilled and unskilled labourers away fighting at the front. The increase of heavy traffic because of the war effort meant that economies and efficiency in transport had to be made wherever possible.

After the signing of the Armistice on 11 November , train ferries were used extensively for the return of material from the Front.

Indeed, according to war office statistics, a greater tonnage of material was transported by train ferry from Richborough in than in As the train ferries had space for motor transport as well as railway rolling stock, thousands of lorries, motor cars and "B Type" buses used these ferries to return to England. During World War II , landing ships were the first purpose-built seagoing ships enabling road vehicles to roll directly on and off.

The British evacuation from Dunkirk in demonstrated to the Admiralty that the Allies needed relatively large, ocean-going ships capable of shore-to-shore delivery of tanks and other vehicles in amphibious assaults upon the continent of Europe. As an interim measure, three to GRT tankers, built to pass over the restrictive bars of Lake Maracaibo , Venezuela , were selected for conversion because of their shallow draft. Bow doors and ramps were added to these ships, which became the first tank landing ships.

It was a scaled down design from ideas penned by Churchill. To carry 13 Churchill infantry tanks , 27 vehicles and nearly men in addition to the crew at a speed of 18 knots, it could not have the shallow draught that would have made for easy unloading. As a result, each of the three Boxer , Bruiser , and Thruster ordered in March had a very long ramp stowed behind the bow doors. In November , a small delegation from the British Admiralty arrived in the United States to pool ideas with the United States Navy 's Bureau of Ships with regard to development of ships and also including the possibility of building further Boxer s in the US.

As with the standing agreement these would be built by the US so British shipyards could concentrate on building vessels for the Royal Navy. The specification called for vessels capable of crossing the Atlantic and the original title given to them was "Atlantic Tank Landing Craft" Atlantic T. This included sufficient buoyancy in the ships' sidewalls that they would float even with the tank deck flooded. In three separate acts dated 6 February , 26 May , and 17 December , Congress provided the authority for the construction of LSTs along with a host of other auxiliaries, destroyer escorts , and assorted landing craft.

The enormous building program quickly gathered momentum. Such a high priority was assigned to the construction of LSTs that the previously laid keel of an aircraft carrier was hastily removed to make room for several LSTs to be built in her place. Twenty-three were in commission by the end of At the end of the first world war vehicles were brought back from France to Richborough Port [12] drive-on-drive-off using the train ferry.

During the War British servicemen recognised the great potential of landing ships and craft. The idea was simple; if you could drive tanks, guns and lorries directly onto a ship and then drive them off at the other end directly onto a beach, then theoretically you could use the same landing craft to carry out the same operation in the civilian commercial market, providing there were reasonable port facilities.

In the period between the wars Lt. Colonel Frank Bustard formed the Atlantic Steam Navigation Company , with a view to cheap transatlantic travel, this never materialised, but during the war he observed trials on Brighton Sands of an LST in when its peacetime capabilities were obvious.

In the spring of The Company approached the Admiralty with a request to purchase three of these vessels. These vessels were LSTs , , and They were renamed Empire Baltic , Empire Cedric , and Empire Celtic , perpetuating the name of White Star Line ships in combination with the "Empire" ship naming of vessels in government service during the war.

On the morning of 11 September the first voyage of the Atlantic Steam Navigation Company took place when Empire Baltic sailed from Tilbury to Rotterdam with a full load of 64 vehicles for the Dutch Government. The first sailing of this new route was on 21 May by Empire Cedric.

After the inaugural sailing Empire Cedric continued on the Northern Ireland service, offering initially a twice-weekly service. Empire Cedric was the first vessel of the ASN fleet to hold a Passenger Certificate, and was allowed to carry fifty passengers.

In another two LSTs where chartered into the existing fleet, Empire Cymric and Empire Nordic , bringing the fleet strength to seven. The Hamburg service was terminated in , and a new service was opened between Antwerp and Tilbury. The fleet of seven ships was to be split up with the usual three ships based at Tilbury and the others maintaining the Preston to Northern Ireland service.

While modest in capacity, it could transport three semi trailers between Hyannis in Massachusetts and Nantucket Island, even in ice conditions. The concept of roll-off stems from the fact that in many networks roll-off tends towards a constant gradient at frequencies well away from the cut-off point of the frequency curve.

Roll-off enables the cut-off performance of such a filter network to be reduced to a single number. Note that roll-off can occur with decreasing frequency as well as increasing frequency, depending on the bandform of the filter being considered: For brevity, this article describes only low-pass filters.

This is to be taken in the spirit of prototype filters ; the same principles may be applied to high-pass filters by interchanging phrases such as "above cut-off frequency" and "below cut-off frequency". This can be shown to be so by considering the voltage transfer function , A , of the RC network: A higher order network can be constructed by cascading first-order sections together.

If a unity gain buffer amplifier is placed between each section or some other active topology is used there is no interaction between the stages. In that circumstance, for n identical first-order sections in cascade, the voltage transfer function of the complete network is given by; [1]. A similar effect can be achieved in the digital domain by repeatedly applying the same filtering algorithm to the signal.

The calculation of transfer function becomes somewhat more complicated when the sections are not all identical, or when the popular ladder topology construction is used to realise the filter.

In a ladder filter each section of the filter has an effect on its immediate neighbours and a lesser effect on more remote sections so the response is not a simple A n even when all the sections are identical.

The ferry itself was built by Thomas Grainger , a partner of the firm Grainger and Miller. At the end of the first world war vehicles were brought back from France to Richborough Port [12] drive-on-drive-off using the train ferry.

Closed On:

As with the standing agreement these would be built by the US so British shipyards could concentrate on building vessels for the Royal Navy. Electronic design Tone, EQ and filter Filter frequency response.

Copyright © 2015

Powered By