For example, semaphore, where the configuration of flags held by a signaller or the arms of a semaphore tower encodes parts of the message, typically individual letters and numbers.

Construction schematic of a Prussian optical telegraph ( or Semaphore line | semaphore ) tower, C. 1835

The Claude Chappe | Chappe semaphore tower near Saverne, France

An old semaphore tower, relief of the former Landau ( and later Strasbourg ) to Paris semaphore line, can be seen in the vicinity.

A Chappe semaphore tower near Saverne, France

* In chapter 10 of C. S. Forester's Hornblower and the Hotspur, the destruction of a French semaphore tower and a shore battery is a key plot point.

* Semaphore Tower Monte Socorro Historical Reconstruction of semaphore tower.

On the site of the yard there is now a building originally used as a semaphore tower, and later used as a coastguard house, then as a timeball tower, which it remains today, and as a museum.

For the next nine months Gina schemes to have Fabrice freed and manages to get secret messages relayed to him in the tower, in part by means of an improvised semaphore line.

In 1804, the clock tower in St Albans signalled news of the Battle of Trafalgar by semaphore.

For example, semaphore, where the configuration of flags held by a signaler or the arms of a semaphore tower encodes parts of the message, typically individual letters and numbers.

Each tower was in sight of the next in the line, and a simple system of semaphore signalling was used between them.

It is based on the semaphore symbols for " N " ( two flags held 45 degrees down on both sides, forming the triangle at the bottom ) and " D " ( two flags, one above the head and one at the feet, forming the vertical line ) ( for Nuclear Disarmament ) within a circle.

Resembling railway signals, they use semaphore arms and are illuminated at night by red and green gas lamps.

A typical solution is to have the task that owns a semaphore run at ( inherit ) the priority of the highest waiting task.

The interrupt handler then queues work to be done at a lower priority level, such as unblocking a driver task through releasing a semaphore or sending a message.

The semaphore arms were augmented by gas illuminated lights at the top ( green and red ) to increase visibility of the signal at night.

From 1803 on, the French also used the 3-arm Depillon semaphore at coastal locations to provide warning of British incursions.

A Popham semaphore was a single fixed vertical 30 foot pole, with two movable 8 foot arms attached to the pole by horizontal pivots at their ends, one arm at the top of the pole, and the other arm at the middle of the pole.

In 1801, the Danish post office installed a semaphore line across the Great Belt strait, Storebæltstelegrafen, between islands Funen and Zealand with stations at Nyborg on Funen, on the small island Sprogø in the middle of the strait, and at Korsør on Zealand.

" I had often seen one placed at the end of a road on a hillock, and in the light of the sun its black arms, bending in every direction, always reminded me of the claws of an immense beetle ..." He later bribes a semaphore operator to relay a false message in order to manipulate the French financial market.

The P operation wastes time or sleeps until a resource protected by the semaphore becomes available, at which time the resource is immediately claimed.

This approach does not work on multiprocessor systems where it is possible for two programs sharing a semaphore to run on different processors at the same time.

Some synchronization mechanism is required at the entry and exit of the critical section to ensure exclusive use, for example a semaphore.

A short length of platform has been rebuilt on the site of the second passenger station ( of 1893 ) at West Bridge in Leicester, and has track alongside it and a semaphore signal,.

The first signalling system on the Norwegian railway system was a mechanically operated semaphore system introduced at Drammen station in 1893.

Ships in formation reverted to pre-wireless methods, including semaphore and signal flags, with signal lamps used at night.

Its signal box, which was formerly at Garve West and transported from there in 1986, was retained when the station itself shut and new features are gradually being brought into service, using traditional British Railways mechanical semaphore signalling, to control a new crossing loop which has yet to be installed.

If the signal being approached is displaying a restrictive aspect ( red, yellow or double yellow in colour-light installations or a distant semaphore at caution ( horizontal ) in mechanically-signalled installations ), the AWS will sound a horn continuously until the driver pushes a button to acknowledge it.

Real geographical locations play a major role: Golden Cap is the site of a semaphore station, and the castle at Corfe is a key presence in the book.

In preparation for electrification, Aston's two mechanical signal boxes, Aston No. 1 and No. 2, were closed, semaphore signalling was replaced by multiple-aspect colour light signals and control transferred to the power signal box at Birmingham New Street.

But this simplistic approach fails when there are multiple levels of waiting: task A waits for a binary semaphore locked by task B, which waits for a binary semaphore locked by task C. Handling multiple levels of inheritance without introducing instability in cycles is complex and problematic.

Deadlock is prevented by careful design or by having floored semaphores, which pass control of a semaphore to the higher priority task on defined conditions.

This is to be distinguished from semaphore which merely transmits messages.

For example, classic semaphores permit deadlocks, in which one process gets a semaphore, another process gets a second semaphore, and then both wait forever for the other semaphore to be released.

This was replaced by a semaphore station, which was part of a semaphore line that operated between 1822 and 1847.

The signal consisted of a semaphore arm ( Manufactured by Saxby and Farmer, who were railway signaling makers ), which was raised and lowered manually by a police constable who would rotate a handle on the side of the pole.

Their semaphore was composed of black movable wooden arms, the position of which indicated alphabetic letters.

One of the principal hills in San Francisco, California is also named " Telegraph Hill ", after the semaphore telegraph which was established there in 1849 to signal the arrival of ships into San Francisco Bay.

When used for a pool of resources, a semaphore does not keep track of which of the resources are free, only how many there are.

The term " binary semaphore " is used to describe a construct which limits access to a single resource.

* Reentrant mutex, which can " count " but in a different manner to a counting semaphore.

* The priority ceiling protocol which is an enhancement of basic priority inheritance which assigns a " ceiling priority " to each semaphore, which is the priority of the highest job that will ever access that semaphore.

While recovering, during which he received a " paltry " pension of £ 45 p. a., he helped his brother-in-law Richard Lovell Edgeworth to construct a semaphore line from Dublin to Galway.

The argument offered by supporters of Morse claims that Morse originally devised a cipher code similar to that used in existing semaphore telegraphs, by which words were assigned three-or four-digit numbers and entered into a codebook.