Signal System

(Russian, signalizatsiia), a system of conventional signs or of devices and accessories used to provide a signal for some purpose. Examples of such purposes are attracting attention, making an announcement, transmitting a command, and accomplishing two-way communication. Signal systems may be visual, auditory, or tactile in nature.

Railroads make use of signal systems (seeRAILROAD SIGNAL SYSTEM), as do such other areas of transport as motor transport (seeROAD SIGNS) and aviation. A graphic panel is an example of a signal system in power engineering. In manufacturing, signal systems are used to indicate the state of machines, machine tools, and production processes; for example, a signal system may compare a production target with the progress made in achieving it (seeTRAFFIC CONTROL). Other uses in manufacturing include the ensuring of safe working conditions. In addition, signal systems are used to indicate that work on a lot of projects is completed and a new lot is required and to warn that the time limits for an operation have been reached or exceeded. The army and navy also make use of signaling.

Signal systems can be classified in various types according to their functional purpose. Cautionary, or warning, systems provide a reminder of the necessity of fulfilling conditions that ensure worker safety and normal execution of production processes. Such systems are also used to control the movement of motor vehicles (seeROAD TRAFFIC REGULATION). Emergency systems provide notification of a failure of normal execution of a production process or make known the stoppage of a machine owing to the appearance of conditions dangerous for its operation; emergency systems may also automatically shut down equipment when such disturbances of normal operation occur (see). Calling, or paging, systems are used to attract the attention of persons being sought or to summon managerial or service personnel to work stations, units, or machines (seeTRAFFIC CONTROL, CENTRALIZEDandFIRE-ALARM SYSTEM). Monitoring and control systems monitor production processes with respect to specified parameters and produce control signals; for example, the level of the liquid in a tank may be monitored by means of indicators or signal lamps. Communication signal systems provide high-speed communication between military units or between enterprises by coded combinations of audio or visual signals; these signals are transmitted directly or are combined with radio transmissions.

Devices used in signal systems include heliographs, road signs, running lights, petards, searchlights, sonobuoys, radiosondes, radio beacons, traffic lights, and semaphores. Signal devices can be operated by mechanical, hydraulic, pneumatic, electric, or radio systems. A mechanical drive may be used, for example, in a semaphore: the arm may be put in position by means of a handle. Hydraulic drives are used in waterworks to control the position of gate valves. In areas subject to fire risk pneumatic drives are employed. Electric drives are used, for example, to control power systems and in railroad transport. Radio systems are used in radar, in radio direction finding, and in radio-meteorological stations.

Additional information on signal systems is given in articles dealing with such subjects as means of transportation, structures, and devices (see, for example, MOTOR VEHICLES, AIRFIELD, andPORT).

in physiology, a system of nervous processes, temporary connections, and reactions occurring in the brain in response to external and internal stimuli and ensuring precise adaptation of the organism to the environment. The concepts of the first- and second-signal systems were introduced by I. P. Pavlov and developed in his work on higher nervous activity.