"UTRL"--AN ELECTRONIC FAIL-SAFE LOGIC IN RAILWAY SIGNALLING

The author begins by explaining the indispensable failsafe requirements of a railway signalling system and how they have been develop from the first mechanical interlocking boxes to the semi-conductor electronic equipment now in use. He then describes how the URTL, which is a dual-channel system, achieves almost total positive security by means of: twin switching units operating in antiphase; comparison of the state of the twin switching units; clockpulse checking of the state of the units; basic elements comprising two identical majority logics; control transducers permeable to signals only if a certain Boole algebra chain is established. A functional unit comprises 30 integrated basic elements assembled on a standard logic printed circuit card.

• Supplemental Notes:
  • Paper read at the IRSE in Brussels on 21/2/75 on the subject of a Siemens electronic logic designated URTL (Uberwachbare Resistor Transistor Logic).
• Corporate Authors:

  Institution of Railway Signal Engineers

  London,   England 
• Authors:
  • Lohmann, H J
• Publication Date: 1975-2-21

Media Info

• Features: Figures;
• Pagination: 11 p.

Subject/Index Terms

• TRT Terms: Fail safe systems; Signal devices; Traffic signal control systems
• Old TRIS Terms: Signal systems
• Subject Areas: Railroads; Safety and Human Factors;

Filing Info

• Accession Number: 00126992
• Record Type: Publication
• Source Agency: International Railway Documentation, Selection of
• Files: TRIS
• Created Date: Nov 18 1975 12:00AM