scope:

GENERAL

The EBI Track 200 TI21 Single Rail version is of the jointed type and is designed for AC or DC electrified areas where high levels of interference (arising principally from 50 Hz harmonics) may be present. The equipment is classified as universal since it meets the onerous immunity requirements of all traction systems and the needs of all known track circuits.

Two different types of track interface can be used:

• End Termination Units (ETU) which have the advantage of providing insulated rail joint (IRJ) failure detection, but have this disadvantage of having to be mounted at the trackside, close to their related IRJ. Details of design rules to enable IRJ failure detection can be found in section 4.

• Track Coupling Units (TCU) which only provide IRJ failure detection when used with double block joints and a transposition bond, but have the advantage of being cabinet-mounted, next to their related Tx or Rx. Details of design rules to enable IRJ failure detection can be found in section 4.

EBI Track 200 TI21 track circuits employ eight audio frequencies in the range of 1549 Hz to 2593 Hz, the nominal frequencies are usually referred to by letter, i.e. frequencies A, B, C, D, E, F, G and H. The usage of the eight nominal frequencies depends on the type of track interface equipment being used.

• With ETUs, the frequencies are used in four pairs - A/B, C/D, E/F, G/H. One pair is used per track and the frequencies are alternated, e.g. 'frequency A' track circuit, then 'frequency B' track circuit, then 'frequency A' track circuit, and so on. Further details of frequency allocation are given in sections 4.2.4 and 4.2.5.

• With TCUs the frequencies are used as groups - A/B/C and D/E/F, and G/H. One group is used per track and the frequencies are alternated, e.g. 'frequency A' track circuit, then 'frequency B' track circuit, then 'frequency C ' track circuit, and so on. Frequencies should not be repeated until a transposition bond is used, with double block joints. The frequencies G/H are reserved for the tracks between cross-overs or where additional tracks are needed to reach a transposition bond. Further details of frequency allocation are given in sections 4.2.4 and 4.2.5.

Standard BR miniature line relays or their equivalent are directly operated by the receiver. It is not necessary to use low powered, high percentage release relays with small contact stacks, or AC immune relays. The TI receiver also has an inbuilt delayed pick-up response that obviates the need for "slow to pick-up" relays .

The transmitters and receivers are arranged for standard BR relay rack mounting.

The EBI Track 200 TI21 TCU track circuit is particularly suitable for use with Single rail traction current return systems within in points and crossing areas