Signaling – Safety System SpDr-64-JŽ for Relay Interlocking

Signalno-sigurnosni sistemDeveloped on the basis of the German system SpDrS-60, it serves as the railway traffic protection in stations with maximum two tracks and interstation dependence. For the safety of the railway stations with lower traffic frequency, the system FSU 90 had been developed. Coordinating signal-safety system KSS-94 serves for protection of railway traffic in stations with maximum four tracks. All signal-safety devices are in compliance with active railway standards and rules. Signal-safety system SpDrS-64-JŽ consits of indoor and outdoor equipment.

Indoor Equipment

Indoor equipment of relay interlocking system consists of command panel, relay and supply unit devices.

Command Panel

Managing of signal-safety devices is done via command panel or command desk from which is possible to determine in each moment the position and condition of main and shunting signals, points, derailers, level crossings etc. On the table of command desk are installed all necessary executive buttons and LED or bulb indicators for monitoring. COMMAND PANEL represent actuall and present track situation in railway station.

Komandni panoCommand panel

Relay Devices SpDrS-64-JŽ

Consists of: frame carriers with rosts, relay frames, cable splitters and inter-splitters, power rails, relay groups, motor
relays and connecting cables.

are modular structures, wired to accommodate certain relays and relay groups. They are locked on relay frame carriers which are fixed to the floor and the walls of the station room. On the relay frame carriers, on the upper side, are built rosts for installing and guiding cables. On the side of the first frame of every line there are 20 power rails trough which power is brought to every line of frames. In frames there are 12 power rails from which are picked powers needed for certain type of frame. Relay groups and relays are installed on typical relay frames. Relay frames are connected with standard cables to inter-splitter and splitter.

Relejni ram na postolju za montažuRelay frame

is used for arranging of all inner cables which are brought from relay frames, command table, power devices and other.

are standardized by function which they do: signal, points, track, indusi balise, activation dependence, for half barriers, dependence on APB etc. Every group type is built on specific frame, on specific provided place. Relay groups are plug in type, from the front side protected with glass panel from external influences and through it is visible condition of the group.

Relejne grupeRELAY GROUPS

In one relay group can be installed a maximum of 35 relays K-50. If any interruption (touch of wires, voltage breakdown) or malfunction of any element happens in the group or irregular work of the relay, signal changes to ,,stop”, and the device goes into the safest condition. Functions of all commands, controls and interdependences are activated through relay devices.


Signalna relea FSU K-50Signal-safety relay K-50 is the heart of the control system of railway signalization. Relay K-50 enables normal and correct functioning of all the elements of electric circuit with high standards in relay reliability. In railway signal technique it is necessary to open certain circuits before closing other circuits, which is achieved by rigid connection of the contacts on relays. Current is certainly interrupted by two serial contact relays. With friction big enough on the contacts it is surely obtained making contacts. Relay K-50 is extraordinary product with many years of experience and constant development.


Excitation side

  • Power max 220 V D.C.
  • Excitation power 0,6 – 1,3 W
  • Work power 1,3 – 2,5 W
  • Time of attracting contacts 25 – 60 ms.
  • Time of releasing contacts 7 – 15 ms.
  • Thermal permanent load 4,5 W
  • Test voltage coil/body 2000 V.A.C. eff
  • Number of coils max 3

Contact side

  • Every contact consists of 2 serial contact places
  • Voltage max 250 VA.C./D.C.
  • Pressure power by contact ≥ 0,15 N
  • Material for contact Ag, Ag/Pd, Ag gal Au
  • Number of establishing and braking circuit > 20×106
  • Permanent current of closed contact 5A

Relay weight is about 220 grams. Position during mounting is horizontal. Allowed slope is about 45º in every direction. Relay K-50 is suitable for work in tropical conditions.

Supporting relay is used in all relay-safety circuits for interlocking and blocking, for instance, main routes, flank protection or other, which in case of network failure or similar event enable us to form the route or direction of route, to remain in position in which they were put.

Supporting (“double”) relay, consists of two normal relay K-50 mechanically coupled with anchors. Relay with anchored lifter remains mechanically locked with anchor of released relay.

Dvostruko spregnuto rele FSU K-50

This relay belongs to bistable relays, stable in two positions depending on excitation, one or the other relay K- 50. It has two coils and two anchors, being each one with it’s own contact system. Contacts of one relay turn off the other, so that is disabled simultaneous powering of both coils. When coils of one relay are excited, at the same time with drawing or releasing of it’s contacts, are released or drawn coils of other relay which remains without excitation.

Command Panel