LS 90

LS is a train control system which is used on the railways in the Czech Republic ( SŽDC ) and Slovakia ( ZSR ). The abbreviation LS stands for Czech Liniový Systém what can be translated as continuous transmission.

LS is installed in the Czech Republic on all main lanes with a speed exceeding 100 km / h in Slovakia on main lines with a speed over 120 km / hr. Most Czech and Slovak drive vehicles are equipped with a vehicle unit that works together with LS.


LS was developed based on the Soviet train control system ALSN and introduced in the early 1960s at the Czechoslovak State Railways ČSD. With LS sat down liquefaction of the operation of the target at any time by the transmission of a changed signal position on the traction unit is independent of the location of the train possible. This requirement caused a system with continuous signal transmission. The system was gradually developed, with the versions LS II, III LS and LS IV are built in relay technology. With LS 90 came at the beginning of the 1990s, electronic circuits used. At the same time the first report on the single European Command ETCS what was decided not to further development of the Czechoslovak train control system appeared. After the separation, only the Czech Republic but saw attached to this decision. In Slovakia, was developed with extended functionality that works together with the Plug equipment of LS with Mirel a vehicle unit. The Czech car unit LS 06 has the same features as the previous versions, but has been updated to the latest technical standards through the use of microprocessors.


The track-side part of the system consists of coded track circuits which operate one carrier frequency. The data transmission between coded track circuits and on-board equipment is via inductively coupled air coil pickup antennae above the rails. On routes operated with 3000 V DC or diesel locomotives, a carrier frequency of 50 Hz is used in AC lines and in stations is the carrier frequency of 75 Hz These two carrier frequencies allow the transmission of four amplitude-modulated signal information (including stop position). The carrier frequency is modulated depending on the position signal one of four different frequencies rectangular. As soon as an engine equipped with a vehicle enters track circuit LS, starting the transmission of the signal information, which shows the signal at the end of the block portion. The vehicle-mounted antennas that are located before the first axis, receive the signal information. The cab display consists of four lights to display the four signal information. Beneath is a more blue light that prompts turned off to service the vigilance.

When driving on sections without LS- wayside equipment that vigilance must be serviced regularly. For sections with LS- wayside equipment, the vigilance is to be operated only upon transfer of signal character caution and 40 and caution. Failing that, sounds after a period of one horn and after a further 4 seconds emergency brake is triggered. A braking distance monitoring does not occur. At speeds below 15 km / h and the handbrake or parking brake vigilance is not active.

Europe standardized successor system

LS will be replaced in the foreseeable future by the European Command ETCS. In the Czech Republic between Kolin and Poříčany a 22 km long, equipped with ETCS Level 2 pilot line. Slovakia operates from Bratislava- Raca to Nové Mesto nad Váhom a distance with ETCS Level 1

LS regard ETCS out as a class B system. For LS a specific transmission module (STM ) is available.