Clock system
A clock or time service system is a device that provides the same time displays in different places.
use
Clock systems are often installed in larger companies or public buildings such as schools, hospitals , train stations or airports . The German railways in particular have operated huge synchronized networks for a long time , in which the station clocks had only minor deviations.
Components
In addition to the power supply, a clock system always consists of the master or master clock and the slave or slave clocks controlled by it. From a slave clock to nationwide clock systems, all intermediate stages are possible. A clock system can be provided with additional signaling devices. Signal receivers of such systems can also be time clocks and time clocks , franking systems , ticket validators or an electronic time announcement . Switching outputs are usually also available for controlling processes that are to be triggered at certain times, such as a pause gong.
If necessary, two or more master clocks can keep each other synchronized as timers. It is also possible to remotely control electromechanical master clocks from a higher-level time service . In the event of a power failure, a follow-up device saves the information about the number of pulses not sent to the slave clocks in order to automatically adjust them when the voltage is restored. Such a follow-up device can be dispensed with in battery-operated systems or systems equipped with an emergency power supply .
Slave clocks
The slave clocks usually only contain a Lavet stepper motor , which is advanced by the signal pulses from the master clock. The slave clocks connected to the same master clock always show the same time, at least as long as there are no technical problems in the network. Corrections, such as the summer or winter time change, are also central and therefore easy to do. The maintenance of the system is considerably cheaper than with a large number of independent single clocks. A separate power supply is required on the slave clock to drive any second hands and to operate the lighting. The faster moving seconds hand is inhibited either mechanically or by electrically switching off the drive when the 12 o'clock position is reached, until the next minute pulse from the master clock advances the minute hand and releases the second hand again for one revolution. A failure of the local power supply of the slave clock only results in the second hand stopping, while the minute and hour hands continue to show the time of the master clock.
Another method are free -running slave clocks operated by a synchronous motor from the mains voltage . B. be synchronized every minute with the master clock by its continuously running second hand ( creeping second ) stops until the defined release by a pulse from the master clock in the 12 o'clock position. To do this, the pointer must run a little faster than the real time during the time between the release pulses. The advantage of this process is that the clock's drive power does not have to be transmitted via the control line. However, a failure of the local power supply of the slave clock leads to the failure to continue and when the power returns, the correct time is no longer displayed without additional measures.
history
In 1839 the physicist and astronomer Carl August von Steinheil invented and implemented the principle of the clock system with a master clock ("normal clock") and slave clock. The main pendulum clock at the University of Munich had a reversing switch, invented by the mathematician and physicist Carl Friedrich Gauß . She controlled a slave clock in the Bogenhausen observatory two kilometers away . Steinheil used the existing two-wire overhead telegraph line . The doubling of the line capacity was achieved by using the earth as a common return conductor for telegraphy and clock.
The first large clock systems came into use in Germany at the end of the 19th century after the German Empire had introduced Central European Time in 1893 at the urging of the railway companies ( law on the introduction of a uniform time determination ). Previously, more than 60 local time orders for individual regions and cities had to be taken into account in the railways' timetables . The railway is therefore considered to be the initiator of a standardization of timing in Germany.
After the Second World War, the Deutsche Bundesbahn set up a network with a master clock at each node with connections to other master clocks. At midnight, the nationwide time adjustment was made by the central clock of the German Hydrographic Institute in Hamburg.
According to the Deutsche Bahn, 2,500 of its 17,000 clocks are currently serving as master clocks. They are designed as radio clocks and receive the signal from the time signal transmitter DCF77 .
With the widespread use of inexpensive radio-controlled clocks, clock systems are on the decline. Especially large systems such as the railways are broken down into small local cells in which the time signals no longer come from a clock center; they are synchronized via the DCF77 transmitter from the Physikalisch-Technische Bundesanstalt in Braunschweig or via comparable time services from other countries ( BEV Vienna, HBG- Sender Neuchâtel, OMA Prague). Radio-controlled single clocks are also often used. However, since no DCF77 signal can be received in many buildings, the clock systems will not be completely displaced by radio clocks in the future either.
Major manufacturers
The clockmaker and entrepreneur Carl Theodor Wagner owned a patent for operating slave clocks. His company also produced for Siemens & Halske (later Siemens AG) and Standard Elektrik Lorenz (SEL), which also sold and manufactured clock systems. Another big name in clock system construction was Telefonbau and Normalzeit (T&N or Telenorma, now Bosch Sicherheitssysteme ). In the DDR clock systems were under the trademark fair RFT or Elfema (electrical feinmechanik Mittweida sold). All of these companies no longer exist or no longer build clock systems.
The Bürk company continued to supply watches until the 1990s. B. for Deutsche Bahn. Today she is part of the Swiss Mobatime . Elektročas (successor to Pragotron) produces clock systems in the Czech Republic . Two large manufacturers remained in Germany: the medium-sized company JUNDES Kaiser Zeitmesstechnik (formerly Jauch and Schmid), which has been making special watches since the beginning of the 20th century, and Robert Bosch GmbH .
Web links
Individual evidence
- ↑ JE Bosschieter: The evolution of electric clocks - B. The first inventors www.electric-clocks.nl, Retrieved on May 8, 2016