RAILROAD SIGNALS of the U.S.
Nomenclature & Symbols
For Signal Drawings
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This section covers the
various circuit symbols used in the signal drawings, and the nomenclature used
to describe them.
The majority of information for this page came from a book labeled Graphical Signal Symbols and Written Circuit Nomenclature, published by The Railway Educational Bureau in 1950, and written D. C. Buell.
This first section deals with the standard AAR abbreviations and nomenclature used in the labeling of relay drawings. If you have ever tried to read a signal drawing, and can't make sense out of it, these "TLA's" should help you.
B Block, button, positive energy (hereafter referred to as power)
C Common, changer, counter, correspondence, circuit, controller, code, checking contacts
D Proceed indication of a signal, detector, decoding
E East, eastward, electric light, element
G Green, signal (operating mechanism), ground
H Home, Approach indication of a signal
J Skate, dual control
L Left, lock preventing initial movement of a lever from normal or reverse position, locking, lever, light, split battery, lock valve
M Lock preventing final or indicating movement of a lever, magnetic, marker
N Normal, north, northward, negative
O Order, operating, off, overload, out
P Pole, power, purple, push, repeating, primary
Q Local or secondary coil (as in double-element relay or mechanism)
R Right, red, reverse, relay, power operated controller or contactor, route, stop indication of a signal
S South, stick, storage, southward
T Track, time, train, telephone, transformer, transmitter
U Retarder, unit
V Train stop (track element), electro=pneumatic stop valve
W Switch (operating mechanism), west, westward, white
X Crossing, interlocking, bell, buzzer, AC
Y Slot, yellow, hold clear
Z Use for any special terms (to be noted on plan)
|EC||Common East, meaning DC from system east (likewise for north, south, and west).|
|FC||Common traffic locking.|
|ENX||Negative voltage AC from POR for lighting, or east negative AC power (likewise for north, south, and west).|
|NX||Negative AC power.|
|BL||Positive side of split battery.|
|NL||Negative side of split battery.|
|CL||Common of split battery.|
|N||Negative of DC power.|
|B||Positive of DC power.|
|EB||Positive power east (likewise for north, south, and west).|
|BB||Battery - second battery.|
|BBB||Battery - third battery.|
|BX||Positive AC power.|
|EBX||Positive AC power from POR for lighting, or east positive AC power (likewise for north, south, and west).|
Units Relating To Track Circuits
|TPR||Relay repeating track relay.|
|TPPR||Relay repeating track repeating relay.|
|TSR||Track stick relay.|
|TSPR||Relay repeating track stick relay.|
|BPR||Block repeater relay, relay repeating the track circuits in a block.|
Wires Relating To Track Circuits
|TB||Track positive - positive power to rail.|
|TN||Track negative - negative energy from rail.|
|RB||Relay positive - wire from positive rail to relay.|
|RN||Relay negative - wire from negative rail to relay.|
|TO||Positive control of local coil, double element AC track relay.|
|TP||Positive control of TPR|
|TPP||Positive control of TPPR.|
|TPS||Positive control of TPSR.|
|TK||Positive control of TK.|
|BP||Positive control of BPR.|
|WB||Positive rail to switch circuit controller.|
|WN||Negative rail to switch circuit controller.|
Operated Units Relating To Switches
|W||Switch operating mechanism or lock valve.|
|WR||Relay, controller, or contactor controlling both normal and reverse operations of a switch or an electric switch lock.|
|WNR||Relay, controller, or contactor controlling the normal operation of a switch or an electric switch lock.|
|WRR||Relay, controller, or contactor controlling the reverse operation of a switch or an electric switch lock.|
|WRPR||Relay repeating WR.|
|WNRPR||Relay repeating WNR or normal position of WR.|
|WRRPR||Relay repeating WRR or normal position of WR.|
|WPR||Relay repeating position of a switch.|
|NWPR||Relay repeating normal position of a switch or normal position of WPR.|
|RWPR||Relay repeating reverse position of a switch or reverse position of WPR.|
|WK||Indicator indicating the position of a switch.|
|WL||Switch lock operating mechanism of a switch.|
|NWLPR||Relay repeating normal position of a switch lock.|
|NJPR||Relay repeating normal position of a dual-control lever.|
|RJPR||Relay repeating reverse position of a dual-control lever.|
|NWK||Indicator indicating the normal position of a switch.|
|RWK||Indicator indicating the reverse position of a switch.|
|WAK||Indicator indicating the condition approaching a switch.|
|RWLPR||Relay repeating reverse position of a switch lock.|
|WCR||Switch correspondence relay.|
Wires Relating To
NW Normal control of switch operating mechanism.
RW Reverse control of switch operating mechanism.
N10W Individual return wire to 10 switch operating mechanism.
WR Positive control of WR.
N10WR Negative control of 10WR.
WNR Positive control of WNR.
WRR Positive control of WRR.
WRP Positive control of WRPR.
WNRP Positive control of WNRPR.
WRRP Positive control of WRRPR.
WP Positive control of WPR.
N10WP Negative control of 10WPR.
NWP Positive control of NWPR.
RWP Positive control of RWPR.
NWLP Positive control of NWLPR.
WK Positive control of WK.
N10WK Negative control of 10WK.
NWK Positive control of NWK.
RWK Positive control of RWK.
WA Positive control of WAK.
WL Positive control of WL.
RWLP Positive control of RWLPR.
WC Positive control of WCR.
NJP Positive control of NJPR.
RJP Positive control of RJPR.
Operating Units Relating To
HR Relay controlling approach indication of a three position signal,
or the proceed indication of a two signal in one arm signaling.
DR Relay controlling proceed indication of a signal.
HDR Relay controlling approach and proceed indication of a signal.
HPR Relay repeating HR or approach and proceed indication of HDR.
HSR Home stick relay controlling the approach indication of a signal.
DPR Relay repeating DR or proceed indication position of HDR.
RGPR Relay repeating signal mechanism at stop.
HGPR Relay repeating signal mechanism at approach.
RHGPR Relay repeating signal mechanism at approach and stop.
DGPR Relay repeating signal mechanism at proceed.
RGK Indicator indicating signal mechanism at stop.
HGK Indicator indicating signal mechanism at approach.
DGK Indicator indicating signal mechanism at proceed.
ETOHR East train order HR (likewise for north, south, and west).
ETOHDR East train order HDR (likewise for north, south, and west).
ETOPHR East train order repeater HR (likewise for north, south, and west).
ETOPDR East train order repeater DR (likewise for north, south, and west).
HDGPR Relay repeating signal mechanism in the approach and proceed position.
HDGK Indicator indicating signal mechanism in the approach and proceed position.
HY Hold clear or retaining mechanism of the approach indication of a signal.
DY Hold clear or retaining mechanism of the proceed indication of a signal.
HG Approach indication operating mechanism of a signal.
DG Proceed indication operating mechanism of a signal.
RG Stop indication operating mechanism of a signal.
Wires Relating To
H Positive control of HR.
D Positive control of DR.
HD Positive control of HDR.
N10HD Negative control of 10HDR.
HP Positive control of HPR.
HS Positive control of HSR.
DP Positive control of DPR.
RGP Positive control of RGPR.
HGP Positive control of HGPR.
DGP Positive control of DGPR.
ETOH Positive control of ETOHR.
ETOHD Positive control of ETOHDR.
ETOPH Positive control of ETOPHR.
ETOPD Positive control of ETODR.
HDGP Positive control of HDGPR.
HDGK Positive control of HDGK.
RGK Positive control of RGK.
HGK Positive control of HGK.
DGK Positive control of DGK.
HG Positive control of HG.
DG Positive control of DG.
RG Positive control of RG.
N10HG Negative control of 10HG.
HY Positive control of HY.
DY Positive control of DY.
RHGP Positive control of RHGPR.
Stick, Traffic, and Directional Operated Units
|ESR||East stick relay, likewise north, south, and west.|
|LSR||Locking stick relay.|
|EASR||East approach sticking relay, likewise north, south, and west.|
|ASR||Approach stick relay.|
|FL||Traffic lock preventing initial movement of a traffic lever from normal or reverse.|
|FLM||Traffic lock preventing initial movement of a traffic lever from normal or reverse and also preventing final or indicating movement of same lever.|
|FLR||Traffic lock relay controlling FL.|
|FLMR||Traffic lock relay controlling FLM.|
|FLK||Traffic lock indicator.|
|FSR||Traffic stick relay.|
|EFSR||East traffic stick relay, likewise north, south, and west.|
Wires Relating To Stick, Traffic, and Directional Operated Units
|S||Positive control of SR.|
|ES||Positive control of ESR.|
|LS||Positive control of LSR.|
|EAS||Positive control of EASR.|
|AS||Positive control of ASR.|
|FL||Positive control of FL.|
|FLM||Positive control of FLM.|
|F||Positive control of FR.|
|FLR||Positive control of FLR.|
|FLMR||Positive control of FLMR.|
|FLK||Positive control of FLK.|
|FS||Positive control of FSR.|
|EFS||Positive control of EFSR.|
Operated Units Relating To Indicators, Locks, Indication Magnets, and Relays Used For Locking Purposes
|M||Lock preventing the final movement of a lever.|
|L||Lock preventing the initial movement of a controlled function or lever.|
|NK||Normal indicator indicating normal position of a unit.|
|RK||Reverse indicator indicating reverse position of a unit.|
|TER||Time element relay.|
|NM||Lock preventing the final movement of a lever to the normal position.|
|RM||Lock preventing the final movement of a lever to the reverse position.|
|NL||Lock preventing the final movement of a lever or a controlled function from its normal position.|
|RL||Lock preventing the final movement of a lever or a controlled function from its reverse position.|
|LR||Relay controlling L lock.|
|LPR||Repeater of L lock relay.|
|MR||Relay controlling M lock.|
|MPR||Repeater of M lock relay.|
|TESR||Time element stick relay.|
|LK||Lock indicator repeating electric locking.|
|TEPR||Relay repeating energized position of TE.|
|TECPR||Relay repeating checking contact of TE.|
Wires Relating To Indicators,
Locks, Indication Magnets, and Relays Used For Locking
M Positive control of M.
L Positive control of L.
NK Positive control of NK.
RK Positive control of RK.
TE Positive control of TER.
NM Positive control of NM.
RM Positive control of RM.
NL Positive control of NL.
RL Positive control of RL.
LR Positive control of LR.
LP Positive control of LPR.
MR Positive control of MR.
MPR Positive control of MPR.
TES Positive control of TESR.
LK Positive control of LK.
TEP Positive control of TEPR.
TECP Positive control of TECPR.
Operated Units Relating To Highway Crossing Signals
|EXR||Eastward interlocking or crossing relay, likewise north, south, west.|
|XG||Wig-wag mechanism - crossing gate mechanism.|
|XY||Slot for wig-wag mechanism - crossing gate mechanism.|
|EOR||Electric light operating relay (flasher relay).|
|XSR||Directional relay to hold crossing signal clear as train recedes from crossing.|
Wires Relating To Highway Crossing Signals
|XG||Positive control of XG.|
|RXG||Reverse control to XG (drive down mechanism).|
|E1||Postive wire to No. 1 unit of flashing light signal (to be designated by letter N, E, S, W).|
|E2||Postive wire to No. 2 unit of flashing light signal (to be designated by letter N, E, S, W).|
|XS||Positive control of XSR.|
|EX||Positive control of EXR.|
|EO||Positive control of EOR.|
Operated Units Relating To Approach And Annunciating Of Trains
|AX||Annunciator indicating approach traffic.|
|EAX||Eastward annunciator indicating approach of eastward traffic, likewise north, south, and west.|
|AER||Relay used for approach lighting.|
Wires Relating To Approach And Annunciating Of Trains
|AX||Positive control of AX.|
|EA||Positive control of EA.|
|E||Positive control of ER.|
AK Approach indicator.
AR Approach relay.
PCR Pole changing relay.
NLPR Relay repeating the normal position of a lever.
RLPR Relay repeating the reverse position of a lever.
E Electric light.
TO Train order.
WTO West train order signal governing westward traffic, likewise north, south, and east.
RR Route relay.
VR Train stop relay.
VSR Train stop stick relay.
VPR Train stop retaining relay.
VY Train stop retaining mechanism.
XR Interlocking relay.
TOR Train order relay.
POR Power off relay.
LOR Light out relay.
ME Marker light.
OR Overload relay.
GDR Ground detector relay.
CT Code transmitter.
DU Decoding unit.
Wires Relating To Miscellaneous
AK Positive control of AK.
A Positive control of AR.
PC Positive control of PCR.
NLP Positive control of NLPR.
RLP Positive control of RLPR.
R Positive control of RR.
V Positive control of VR.
VS Positive control of VSR.
VP Positive control of VPR.
VY Positive control of VY.
X Positive control of XR.
TO Positive control of TOR.
PO Positive control of POR.
LO Positive control of LOR.
ME Positive control of ME.
O Positive control of OR.
GD Positive control of GDR.
CT Positive control of CT.
DU Positive control of DU.
This section deals with symbols used on signal drawings.
Signals and Semaphores (prior to
Searchlight and Color Light Signals (prior to ~1950)
Signals, Semaphores, & Smashboards
Relays - DC & AC
Circuit Controller Contacts - Miscellaneous
Circuit Controller Contacts
Contacts Actuated By Switch Points, Derails, or Locking Connections
Other Signal & Pneumatic
Indicators, Locks, Buzzers, & Bells
Other Electrical Schematic Symbols
Railway Tracks & Highway Crossings
Buildings, Bridges, & Tunnels
Miscellaneous Devices Applied To Tracks
Pipe and Wire Lines
Lead-Outs, Bolt Locks, Cranks, and Deflecting Bars
last Changed: 26-Aug-2013