Type B Vital Relays - Alstom

Glossary
B. APPENDIX B - GLOSSARY
B.1.
CONTACT DEFINITIONS
Back – (B) Relay contact that is made when relay is de-energized (normally closed).
Break - All front or back contacts are just open when a gauge of a specific dimension is
inserted between the armature residual screw and the core face with the relay
energized.
Break-before-make -In a dependent front-heel-back contact the back contact will break
before the front contact makes as the relay is energized.
Contact Application
• D = Dry Circuit
• EHD = Extra Heavy-Duty
• HV = High Voltage
• HD = Heavy-Duty
• LD = Light Duty
• MD = Medium Duty
• S = Safety
• XHD = Heavy-Duty with Blowout Magnets
Contact Materials –
• AgC = Silver Impregnated Carbon
• AgPt = Silver Platinum
• G = Gold
• S = Silver
• SCdO = Silver Cadmium Oxide
• T = Tungsten
Front – (F) Relay contact that is normally open when relay is de-energized.
Heel – (H) Contact that is driven by pusher.
P1457, Rev. Nov/07 B–1 Alstom Signaling Inc.