1.5 Relay Letter Symbols

In accordance with American National Standards Institute Y32.2-1975, the following letter symbols may be used with any relay symbols to show the special features a relay possesses.

ac Alternating-current or ringing relay ML Magnetic-latching (remanent)
D Differential NB No bias
DB Double-biased (biased in
both directions		 NR Nonreactive
DP Dashpot P Magnetically polarized
using biasing spring,
or having magnet bias
EP Electrically polarized SA Slow-operate
and slow-release
FO Fast-release SO Slow-operate
L Latching SR Slow-release
MG Marginal SW Sandwich-wound to
improve balance to
longitudinal currents

The term "slow" and "fast" are relative, and the degree of rapidity is not to be implied by the use of the symbol on a relay. Relays that are dc operated are not marked.