Type B Vital Relays - Alstom

General Description
1. SECTION 1 – GENERAL DESCRIPTION
1.1. INTRODUCTION TO VITAL RELAYS
For over 70 years, Alstom Signaling, Inc. has continually perfected the Type B relays.
They are the standard relay of the signaling industry. Types B and VTB plug-in relays
meet applicable manual parts of American Railway Engineering and Maintenance of
Way Association (AREMA).
Alstom Type B plug-in relays are used in vital circuits, and are rack-installed in
equipment rooms and in wayside cases and housings. These relays are divided into two
sizes, B1 and B2, as shown in Figure 1–1. Some B relays are energized by DC voltage,
others by AC voltage. A vital relay is designed so that the probability of its failing to
return to a prescribed state when it is de-energized is so low that for all practical
purposes it is considered to be nonexistent.
ALS
ALS
B1 RELAY
B2 RELAY
Figure 1–1. Alstom Type B1 and Type B2 Type Vital Relays
There are more than a dozen types of Type B relays, available in about 200
configurations. They are designed to meet the important requirements of safety,
reliability, low maintenance and long operating life. Replacement parts for relays
decades old may still be available should it become necessary to extend their operating
life. Alstom furnishes its customers relay application and adjustment instructions, either
as part of a contract or upon request.
P1457, Rev. Nov/07 1–1 Alstom Signaling Inc.