Usually the following test signals are used:
Prior to 1969, the code was much more extensive, covering a wider range of messages and including a list of five-letter codes for every prominent maritime location in the world. Since 1969, it has been reduced to focus on navigation and safety, including a medical section. Signals can be sorted into three groups:
In both systems, line numbers 17 and 18 are assigned for VIT signals in each field. (These line numbers are used just for the first field. For second field, they correspond to line 280 and 281 in system M, and line 330 and 331 in system B.)
In some cases, additional characters are added to indicate quantities, bearing, course, distance, date, time, latitude, or longitude. There is also provision for spelling words and for indicating use of other codes. Several of the more common single-letter signals are shown at the right. Two-letter signals cover a broad gamut of situations; the interested reader is urged to download a copy of the Code from the link below.
Signals are erected at intervals of approximately a quarter mile (400 m) along the affected area. There are seventeen signals in all. They are numbered from "1" to "17", with signal 1 being at the east (Dalmally) end. All except number 9 stand on the south side of the line. All the signals apart from numbers 1 and 17 carry two semaphore arms, one for each direction. The signal arms usually all stand in the 'clear' position.
On the Hokuetsu Express Hokuhoku line (with high-speed signals), two repeating signals are used vertically; both signals display vertical lines for high speed. For other signals, only the lower repeating signal is used.
Many semaphore signals were formerly used, which were controlled by a hand lever. Few semaphores remain in Japan. On 28 July 2005, the last semaphore signals on the JR lines at Rikuchū-Yagi Station were replaced by colored lights. A few stations are still equipped with semaphore signals on the Tsugaru Railway Line, the Fukushima Rinkai Railway Main Line and the Niigata-Higashi industrial line.
Home, starting and block signals on Japanese railways are usually lights composed of three colors (green, yellow and red). The composition of the lighted colors shows the speed limit of the protected section.
Electronic signals intelligence (ELINT) refers to intelligence-gathering by use of electronic sensors. Its primary focus lies on non-communications signals intelligence. The Joint Chiefs of Staff define it as "Technical and geolocation intelligence derived from foreign noncommunications electromagnetic radiations emanating from sources other than nuclear detonations or radioactive sources."
Temporary signals (臨時信号機, rinji shingōki) are installed in work areas to indicate temporary speed restrictions. Whilst these resemble signs, they are technically classed as signals.
An advantage of this design over the standard distant signal of the Reichsbahn was that it displayed a clearly visible signal aspect in each position. As a result, it did not need a distant signal board (Vorsignaltafel). This was hesitantly retrofitted by the Reichsbahn from 1936. After the Second World War, however, distant signals without signal boards could still be found in Bavaria.
From 1922, the night aspects of Bavarian distant signals corresponded to the standard Vr 0 and Vr 1. Until 1922, however, a green light meant 'caution'. For the 'clear' aspect, the green lens was folded away and a white signal lamp appeared. The Bavarian distant signal was unusual in that it only knew two aspects. 'Caution' always meant "expect a stop signal". In addition, to begin with, a distant signal was only installed, if the home signal could not be seen within the train's braking distance.
A passing signal has no red light. With multiple starting signals, there are also multiple passing signals with a one-to-one relationship.
A distant signal (遠方信号機, enpō shingōki) is installed before a home signal with limited visibility and is linked to the home signal. Distant signals are primarily installed in non-automatic block sections on single-track lines. They may have two (caution and clear) or three (caution, reduced-speed and clear) displays. With multiple home signals, the distant signal applies to all.
The blade portion of the semaphore was of several designs, each conveying a different meaning: - Those with a square end are "absolute" signals and generally force trains to stop when in their most restrictive position. - Those with a pointed end are "permissive" signals and permit a train to continue at a significantly lower speed rather than having to come to a complete stop. - Semaphores with a "fishtail" end (that is, a V-notch end) are "distant" signals conveying to the engineer what the aspect of the next signal is (as a forewarning). The color of the semaphore frequently matches the above categories as well, with absolute signals typically having a white stripe on a red blade and the others having a black stripe (most often repeating the shape of the blade's end) of either square or 60 degree, were the RSA Standard.
Hall's response to this (for them) dire situation was to buy the 1918 filed patents from one Mr. Blake for his "Searchlight" signal. In reality, the searchlight signal was an updated and modernized variation of the old Hall enclosed disc signal. What Blake had done was to harness the standard railroad three position polarized vane relay, add a miniature spectacle and Pyrex, low expansion Borosilicate glass roundels, and couple that with a very efficient elliptical reflector and optical lens system with a very large 10-1/2 diameter stepped outer lens. This revolutionary development, provided a signal with a visible indication of over a mile from the signal in broad daylight, when the signal was located on tangent track. The early color light signals were visible for only about half that distance (2,500 feet) while using about the same current consumption, then a major concern in "Primary Battery Territory." By 1925, the development of "High Transmission Colors" of railroad glassware by Dr. Gage and Corning Glass improved this limited distance to an acceptably competitive 3,500 feet on tangent track.
FISINT (Foreign instrumentation signals intelligence) is a sub-category of SIGINT, monitoring primarily non-human communication. Foreign instrumentation signals include (but not limited to) telemetry (TELINT), tracking systems, and video data links. TELINT is an important part of national means of technical verification for arms control.
The 1911 patenting of the "Doublet-Lens" combination for long range (2,500 feet in daylight) by Dr. William Churchill at Corning Glass's research facility in Corning, New York, indicated the reign of the semaphore signal in railroad use was rapidly approaching its end. By 1916, this optical combination and a flagging sales response prompted the management of the Hall Signal Company to realize their just introduced and most advanced Style "L" semaphore mechanism (the very last produced by any U.S. signal company), was indeed obsolete. That dual lens device had been developed by Cornell University's Dr. William Churchill, while he was working at Corning Glass Works. He'd finished developing color standards for railroad glassware, which Corning had patented on October 10, 1905. They were immediately put to use as daylight short range and tunnel type electric incandescent bulb illuminated signals. He then turned his attention to medium and long range Daylight signals using the same incandescent electric lamps using greatly improved optics: the "Doublet-Lens" combination.
The motor-controlled North American semaphores used since the advent of the track circuit block system of 1872, provided a form of automation sought after by the railroads to reduce labor costs and improve reliability over manually operated systems as in the UK, Germany and elsewhere. Dwarf signals were worked mechanically, pneumatically to give restricting-type signals as did mast type signals at interlockings, but motorized dwarfs were more common after the development of the Model 2A signal in 1908. As early as 1915, the technological push by -such intellectual giants as A.H. Rudd of the Pennsylvania R.R. and his concept of speed signalling combined with his development of the Position Light signal and the concurrent color-light signals using William Churchill's doublet lens combination in practical terms made the semaphore technically obsolete.
Searchlight signal's use became widespread mostly due to their relatively low maintenance, high visibility, low power-consumption, and after 1932 using a compound lens with a 4 watt, 3 volt bulb, that worked quite well in territory with battery powered signaling. Also of significance was the single lens giving the indications in multiple head interlocking signals in a fixed location with regard to the mast and the other signal heads, this not being the case with multiple lenses color light signals. In time the costs of the significantly more expensive searchlight signal's relay began to outweigh the savings from its compact size and single bulb when compared with the simple multiple lensed color light signal. By the end of the 1980s the searchlight had lost its position as the most popular signal style in North America.