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The Universal Fail Safe Block Interface Equipment UBX -2000 is meant for interfacing various signaling information of a block instrument at one end of a block section and exchanging them with the block interface equipment at the other end through a digital transmission equipment (optical or radio) ensuring high degree of safety and availability.


Safety of a block instrument is ensured by a foolproof logic sequence and relay interlocking. Safety for the Block Interface Equipment means it must correctly acquire the signal and reproduce it at the other end without any error. In case of any failure, it is detected and the system is lead to a fail -safe state.


However, there are some very remote possibilities when t he system may not be able to detect a failure which may lead to an unsafe situation. This is defined as Mean Time between Wrong side Failure (MTBWSF) and according to RDSO specification SPN 147/2005, the figure is 10 9 hrs. This can be very well ensured by using 2 out of 3 hardware redundancy logic at the I/O Interface and processor level. With 2/3 redundancy system, as soon as an anomaly is detected, the system is forced to a fail -safe state leading to a RED signal. Mishaps are thus avoided, but the mov ement of the train is also restricted. To increase the availability of the system, thus triple hardware redundancy has been proposed at the I/O interface and Processor level so that even if a failure is detected in one set of hardware fail safe operation can still continue with 2 sets of hardware, thereby increasing availability. Better availability is also ensured by using dual redundant power supply unit for the system.



  • Designed for fail safe operation.

  • Triple redundant hardware at all levels with 2/3 decision logic ensures high degree of safety as well as availability.

  • System meets CENELEC & ORE 155 guidelines for safety and reliability.

  • System meets RDSO specification SPN-144 and SPN-147/2005 for all types of Block Instruments in operation in Indian Railways.

  • Simple, modular and rugged design.

  • High performance 16 bit Intel 80C196KC Microcontroller used for better software management.

  • CMOS/FET active components to ensure low power consumption and better reliability.

  • Hi-rel components, relays and connectors used to ensure high MTBF.

  • All input-output connections are optically and/or galvanically isolated to eliminate ground noise and earth faults.

  • Rugged communication protocol for transmission of error-free data.

  • Dual power supply in hot-standby mode increases system availability.

  • 16-digit dot-matrix alpha-numeric display for user friendly man -machine interface.

  • Environment specification meets IS-9000.


Safety and Availability are the two keywords which are reflected in all the stages of the system design.

The system is housed in a 19 inch subrack, 6U (10.5 inches) high, which is fixed inside a closed rack of approx 5 ft high. The front panel of the closed rack is a hinged door fitted with transparent plastic sheet so as to enable the operator to see the LEDs and displays of the system. The door is also provided with a lock to protect the system from unauthorized access. The rear panel of the closed rack is normally fixed with screws. The various cards which have been used in the system are as follows:

Power Supply Unit
System Module
Communication Driver Unit
Relay Input Interface Module
Relay Output Module
Relay Feedback Module
Display and Reset Panel
Alarm Extender Module
Alarm Panel For SM

The above modules are housed in a passive backplane which has the provision of accommodating 12 modules. The basic system consists of two power supply units connected back to back, three system units and one communication driver unit. The above modules consume six fixed slots. The subsequent six slots are for accommodating two nos. of each of Input, Feedback and Output modules. The last slot is not used.

The position of the power supply unit, the system unit and the communication driv e unit is fixed on the backplane. To avoid insertion of wrong card in a slot, the connectors have relative offset so that only the right card will be accepted in the right slot. Input, Output and Feedback module have fixed position on the backplane.
The backplane accepts two input modules in slot 7 & 8, two feedback modules in slot 9 & 10 and two output modules in slot 11 & 12. Input signals received through slot 7 will be output through slot 11 at the other end of the UFSBI system. Feedback of output signal of slot 11 is taken through the feedback module of slot 9. Thus the three cards of slot 7, 9 & 11 forms a composite set of first 8 input / output. Similarly the three cards of slot 8, 10 & 12 forms a composite set of rest 8 input / output.
The each of the I/O Modules has triple redundant hardware for the same external I/O signal to ensure the safety and availability of the system. These I/O modules are interfaced to the three processors through three separate universal I/O bus. The degree of saf ety specified is ensured not only by hardware but also by software taking inputs and feedbacks from various stages of the system.
All the alarms and status of the system are displayed with various onboard LEDs on each of the modules. Further a 16 character alphanumeric display panel/module is used to prompt the various alarm conditions with short mnemonics for easy understanding of the problem. The display panel is fitted at the top of the subrack and is common for all the three processors. In case of a larm in the system a piezo buzzer is activated to draw the attention of the operating staff. Acknowledgement of alarm through a key on the display panel stops the buzzer but the alarm is still displayed on -line as long as it is continued. The display panel also accommodates external resetting provision and the veeder counter for registering these resets.
The Alarm Extender Module provides alarm indications to the SM’s Panel and relay contacts for external data logger for logging various alarm conditions . It also performs the optional signal amplification for combating cable losses ( upto 30dB ) when two UFSBIs are connected through QUAD cables.
The Q-series relays for interfacing various I/O signals are fitted in a panel at the bottom of the closed rack. Wiring of the various external relays of the Block Instrument for interlocking are done through the front and back contacts of the Q-series safety relay inside the rack.

System related information:

This equipment is capable of driving safety signaling relays conforming to specification BRS:930 (QSeries).
The equipment is capable of working on Telecom Cable as well as Voice Channel provided over Optical Fibre or Microwave systems.
This interface equipment conforms to the voltage and current requirements , impedance matching and other electrical characteristics of the block instrument (SGE type).
The coding of signal transmission takes care of types of noise generally encountered in the transmission system and ensure safety of operation against these noise .
Each interface equipment in the section has a unique address which is settable through backplane jumpers.
The information exchanged between the pair of the interface equipment contains the source & destination address.
Wrongly addressed information pac kets are promptly rejected by the system.
The bell of the Block Instrument shall work on E/M signaling of Voice Channel. Alternatively, the bell may be worked through this.
The block telephone will work on a separate voice channel.
The system works on 24V (+20% to -10%).
The resetting facility has been provided in the Display and Reset Panel to bring back the UFSBI into normal operation which has gone into shutdown state. The procedure for resetting has been provided in the functional description of Dis play and Reset Panel under the heading “Procedure – Reset Operation”.
SYSTEM CONFIGURATION   Triple redundancy at all levels including processor
CENTRAL PROCESSOR   Hight Performance 16 bit Intel 80C 196KC Microcontroller
Hardware : CENELEC EN 50129
    ORE 155.A
    RSDO SPN 144 & SPN 147 / 2005
Software : CENELEC EN 50128
Input Module   16 change over input, Opto isolated with transient suppressor
Output Module   16Q series Relay output with 8F / 8B contacts
    Transient protected
    Short circuit protected
Note: Output module needs an Input module for getting feedback from the external signaling relay driven by the system.
FSK, V.23   1200 Baud
4QAM V.22.bis   2400 Baud (not used)
Send level   -8 dBm nominal
Receive Level   -12 dBm nominal
S/N Ratio   better than 20dB for BER 10-6
Configuration   Hot-standby
Input   24 V DC nominal
    21.6 V DC to 28.8 V DC
Output   +5.8 V Dc, +- 0.3 V, 1.5 AMPS (Int)
    +12.8 V Dc, +- 0.5 V, 4 AMPS (Int)
Consumption   20 Watts (nominal) for basic system
(excluding the activation drive of external signaling relays)
Protection   Input : Surge and transients, Overvoltage alarm, Over voltage shutdown, Undervoltage alarm, Undervoltage shutdown
    Output: Overvoltage and short-circuit
Efficiency   >70% at optimum load
ENVIORNMENT   QM333 Catagory B2
Temparature   As per RDSO/SPN/147/2005
Humidity   As per RDSO/SPN/147/2005
MECHANICAL   Sub-rack of UBX 2000 is 19" wide, 6U high
Closed Rack (standard) is 600mm wide, 32U high


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