P
Palladium, 245, 441, 521, 524, 537–538
contact resistance behavior of, 458
Palladium-based alloys, 1204
Palladium-based plated contacts, contact resistance of, 473
Palladium-based systems, 465–466
Palladium–nickel alloys, 460, 521, 524
Palladium–palladium contacts, 469, 471
thickness, 523
Palladium rider sliding, 419
Palladium–silver alloys, 458
Palladium switching contacts, 940–942, 1204
palladium silver, 941
Palladium vs. gold alloys, 460–462
Palliative measures, power connectors, See Power connectors, palliative measures
Panel type connector, 378
Paper electrography, 528
Parabolic tarnish kinetic equation, 115
Parallel arc fault, 854
Paschen curves for air and SF6, 564, 565, 855–856
Paschen’s law, 564
Passive Intermodulation (PIM) interference, 1112
PCBs, See Printed circuit boards
Percussion welding, 654–657, 903–904, 965
Perfluorinated polyether (PFPE), 180, 488
Perfluoroalkyl polyether fluid, 495–496
Permanent magnet (PM) motor, 1086, 1088
Permanent power fuse, 821
Permittivity vs. dust deposition density, 202, 203
Peroxides, 117
Petrolatum grease, 503
PFPE, See Perfluorinated polyether
Photoelectric emission, 566
Photovoltaic solar power systems, 637, 647–648
Piezoelectric actuation in MEMS, 705
PIM interference, See Passive Intermodulation interference
Pip and crater formation, 638, 757, 889, 901–902, 980
Planck’s constant, 54
Plasma state, 554, 556, 826, See also Arc column
creep and, 305
Plasticity index, 76
Plated contacts, 23, 131–132, 253–256, 414–505, 520–545
Plating-factor, 25
clad, 521
classification of, 244–246, 523–526, 688–689
ENIG, electroless Ni and immersion Au, 423
intrinsic polymers on hard gold, 525
iridium, 689
other deposits, 525
palladium and palladium alloys, 245, 523–524, 714
platinum, 714
tin, 525
tungsten, 689
electroless, 522
electrolysis, 522
gold over carbon nano-tubes, 714–717
Kerkendall porosity, 532
porosity, See Porosity
power connectors, 246, 253, 331–333
substrate diffusion, 532
Platinum-based alloys, 1204
Platinum plated contacts, 245
thickness, 523
Platinum switching contacts, 942–943, 1204
Plots of formative time lag vs. fractional over voltage, 571
Pneumatic contactors, 794
Point-on-wave (POW), using Ag/CdO contact materials, 771–773
Polyglycol diproxamine D157, lubrication with, 177
Polymer-forming materials, 457
Pore corrosion, 120–122, 153, 262, 526, See also Corrosion and Porosity
corrosion product, 114
classic test, 423
corrision product, 114
origins of, 527
methods B735, B741B799, B809 (ASTM), 528
porous gold, 153, 161, 162, 423
properties related to, 526
thickness of finish, and substrate roughness, 529–530
underplatings, flash coatings, and strikes on, 530–532
Position sensor connector, automotive, 402
Possible mechanism of energy transfer at cathode and anode, 584
Potential energy vs. distance for electron, 566
POW, See Point-on-wave
Powder metallurgical (PM), 887–890
Power connections, installation, 361–363
dead end, 327
insulation piercing, 236
intermetallics formation in, 298–299
physical model, 351
plug and socket, 236
shape memory (SMA), 327–331, 351–355
Souriau, 354
stepped deep indentation, 315–316, 344–345
thermite welding, 339
wedge, 325
wire, 236
Power connectors, palliative measures, 264, 306
mechanical contact device, 320–322
multilam contact elements, 338–339
Power connectors, performance factors, 233, 247
aluminum and aluminum alloys, 243–244
copper and copper alloys, 240–243
corrosion, See Corrosion
creep, See Creep, metal
current cycling tests, 315–316, 333, 345, 363–365
elastic deformation, 253
electric current effect, 301–302
factors affecting reliability of, 247–249
fretting, See Fretting installation, 361–363
intermetallic compounds, See Intermetallic compounds
nut factor, 319
plastic deformation, 252
stress relaxation, See Stress relaxation
thermal expansion, 264–267, 321–322
thermoelastic ratcheting effect in bolted aluminum joints, 266
testing, 363
disturbances, 347
harmonic distortions, 348
interruption, 348
sag, 348
swell, 348
transients, 347
Pre-impact arcing, 570, 631, 654, 775–776
Preoxidized metal oxide parts, 887
Pre-strike arc, 570, 631, 654, 775–776
Primary cathode spot parameters, 594
Primary interface interactions, 1098
Primary operating conditions for electromigration, 124
Printed circuit boards (PCBs), 423
Probability of anode spot formation, 594
Probe contacts, 543
Prognostic models for power connectors, 349–351
Progressive subsurface plastic deformation, 428
Prow formation, 415, 419–421, 437, 1103
Purple plague, 132
Q
Quantum-mechanical tunneling mechanism, 567
Quenching principles (arc)
low-voltage circuit-breakers, 808–810
Quenching systems (arc), 787–788
R
Race theory of dielectric recovery, 599
Rack type connector, 378
Radial brushes, 1050
Radial stresses, 73
Radiation, low-voltage arcs simulation, 825–826
Radioactive tracer contact erosion measurement, 639, 640
Radio-frequency interference (RFI), 1087
Radio frequency microelectromechanical system (RF MEMS), 703
Real contact area, 15, 249–251, 1042
vs. apparent contact area, 15, 249, 1128
Reasonable noise specification, 1138
Reed relays and switches, 674–698
contact adhesion prevention, 695–696
contact surface treatments 690–693
drop-out characteristics, 682–683
ground plating layer, 687
magnet drive characteristics, 683–686
neutral position detection switch, 700
oxygen, 693
polymerization, 690
pull-in characteristics, 674–682
thermal, 701
Reflection high-energy electron diffraction (RHEED), 693
Reignition voltage, 599, 637, 800, 801, 832–834
arc chamber wall material effect, 799–800
Relative humidity (RH), 117–118, 126, 127
Residential low current arcing faults, 871
Residential wiring, 869
Residual resistivity, 238
Resistance welding, 341
wire-welding, 963
Reynolds equation, 721
RFI, See Radio-frequency interference
RF MEMS, See Radio frequency microelectromechanical system
RH, See Relative humidity
RHEED, See Reflection high-energy electron diffraction
Rhenium, 686
Rhodium oxide (Rh2O3), 693–695
Rhodium-plating solution, 687
Richard-Dushman equation, 566
Rigid noncurrent-limiting breakers, 812
Ring temperature, coefficient of friction vs., 1053, 1054
Rivets, See Contact rivets Rockwell hardness, 1196
Roughness, surface, 431
Round dots, 521
S
SAE, Society of Automotive Engineers, 377
SAMs, See Self-assembled monolayers
Scanning electron microscope (SEM), 29, 187, 716
Scanning electron microscopy with energy-dispersiveX-ray spectroscopy (SEM/EDAX), 129
Scanning Tunneling Microscope (STM), 1111, 1141
SCC, See Stress corrosion cracking
Scintillations, 855
Second Townsend coefficient, 563
Self-assembled lubricant layers, 500–503
Self-assembled monolayers (SAMs), 502
Self-healing, 504
of electrical contacts, 75, 96
process, 256
Self-induced fields, switch arc motion control, 998
SEM, See Scanning electron microscope
Series-wound field motor, 1086
Servomotors, 758
SFA, See Surface forces apparatus
Shape-memory alloy (SMA), 351–355
and disc-spring washers, 329–331
Shape-memory effect (SME), 327
electronic application, 329
two-way, 353
Sharp contacts, 543
Sharvin resistance, 81, 83, 210, 708, 1110–1111
heating effect, 82
role in small aluminum-aluminum contacts, 86–87
Shear-induced ordering transitions, 1102
Sheet clad metal, 521
Shielding effects, 147
corrosion, 134
critical fields, 568
electron emission, 566
enhancement factor, 568
SI, International System of Units, 1207–1208
Signal quality, 1094
Silicone contamination, arcing contacts, 665–667, 1018–1030
lower molecular weight fractions, 1019
lubricant, 1024
migration, contamination from, 666–667, 1023–1029
SEM and EDX analysis, 1029
silicone migration, 665–667, 1023–1029
silicone vapors, 665–667, 1019–1023
types of, 1018
vapors, contamination from, 665–667, 1019–1023
corrosion mechanisms, 151
Silver alloys, 1202
noble metals, See Noble metals
non-noble, See Non-noble silver alloys
Silver-coated contacts, stability of, 287
Silver coatings, contact properties of, 339
voltage drop across, 642
silver-based alloy switching contacts, 937–938, 1202
silver-based switching contacts, 939, 1202
Ag-Cu, 938
Ag-Ni, 939
Ag-Pd, 940
Ag-Pt, 942
Silver counterface, 1132
Silver-graphite brushes, 1084
Silver graphite switching contacts
dynamic welding, 944
erosion rate, 922
Silver metal oxide switching contacts, 802, 880–908, 1203
AC vs. DC testing, 890
erosion/arc, 632, 644, 896–902, 904–906
erosion/arc mobility, 906
erosion/materials transfer/welding, 899–902
erosion/mechanisms/cracking, 904–906
interpreting Ag-CdO material research, 895–899
interruption characteristics, 800, 906
manufacturing technology, 884–895
materials
Ag-Fe2O3, 899
Ag-MgO-NiO, 883
Ag-SnO2, 632, 644, 883, 889, 891–894
silver–cadmium oxide vs. silver–tin oxide, 895
thermal arrest lines, 886
Silver migration, 124
Silver nickel contact materials
electrical erosion, 939
manufacturing methods, 881
Silver-plating, 244, 332, 439, 524
Silver-refractory metals, 908–935, 1203, 1205
arc erosion, 919
contact resistance, 663, 928–935
electrical properties (EP), 918
graphite additions, 922
manufacturing technology/press sinter repress, 909–910
materials
material properties, 908, 1203
metallurgical/metallographic methods, 912–914
metallurgical/structure/strength and toughness, 914–918
oxides and tungstates, 663, 928–935
Silver–silver contacts, 450, 661
growth rate and electrical resistivity, 52–54, 142–143
Silver tungstates, 663, 930–935
Silver whisker, 542
Single controlled bounce, 656
Single-gas corrosion effects
hydrogen sulfide, 159, 161–162
Single gas mixtures, 131
Single-wafer brush, 1090
mass transfer between contacts, 644
Skin effect/depth, 240
and constriction resistance, 89–95
electromagnetic penetration depth, 90
Sliding contacts for instrument control, 1094–1143
adventitious lubrication, 1121, 1124
anaerobically lubricated contacts, 1122–1123
anaerobic vs. aerobic lubrication, 1121
cantilever composite brush, 1128–1129
cantilever metallic finger, 1129
cantilever wire brush, 1129–1130
conductivity, 1134
contact impedance, 1096, 1112–1113
contact resistance variation (noise), 1108–1109
contaminating environment, 1121
cylindrical surface, 1127
data integrity, 1114
direct effect torque, 1135
disjoining pressure, 1122
dynamic effects, 1107
electrical performance in, 1107–1108
excessive static friction, 1135
film formation on a-spots, 1115–1117
filming properties, 1134
film potentiometers, 1133
flammable fuels, submerged in, 1125
flat counterfaces, 1127
fluid-lubricated wire brushes in V-grooves, 1125
fretting, 1124
frictional polymers, 1124
friction and wear characteristics, 1135–1138
gas lubrication, 1125
groove configurations, 1127
guidelines, 1114
hard particle/three-body, 1105
inductance in contact region, 1114
low pressure and vacuum operation, 1125
macro, See Macro sliding contact
mechanical action, 1117
micro-cuts, 1139
micro-environment of contact region, 1114–1115
micro-interrupts, 1139
molybdenum disulfide, 1125, 1133
motion continuation, 1102
motion initiation (pre-sliding), 1100
non-linear noise (frequency dependent), 1111–1112
numerical modeling, 1103
over-lubrication of sliding electrical contacts, 1122
particulates, 1117
passive circuit elements, 1114, 1139
pin-on-disk contact, 1126
platter slip ring, 1140
polymeric films, molecular re-ordering in, 1100
potentiometers, 1127
pressure, 1135
resistive effects, 1114
ring sliding system, 1056
sawtooth stick-slip curves, 1101
spring force, 1128
spring properties, 1134
stick-slip process, 1101
temperature extremes, 1124–1125
tunnel resistance and vibration, 1048–1051
types of, 1044
unintentional contamination, 1117–1119
voltage drop, 1059
water molecules, 1118
Wexler’s formula, 1111
Sliding contacts, metal fiber brushes, See Metal fiber brushes
arcing and bridge transfer, effect of, 1169–1170
critical/transition brush pressure, 1163–1164
film disruption, 1172
Holm-Archard wear equation, 1158–1159
low wear equilibrium, 1159–1160
sliding speed effects, 1166–1169
steady state flash temperature, 1169
wear vs. brush pressure, 1164
Sliding graphite based contacts, 1042–1077
adhesive wear, 1048
atoms, layered structure of, 1074–1075
brush materials and abrasion, 1067, 1073–1076
contact area, 1042
elastic penetration, 1047
electrical noise, 1087
friction-excited vibrations, 1049
graphite crystal structure, 1075
Hertz’s formula, 1045
Holm’s law of wear, 1048
Holm’s wear equation, 1071, 1072
homo-polar bonds, 1074
ideal commutation, 1082
Kohlrausch-Holm Method, 1065–1066
mechanical contact surface, 1064–1065
metal/graphite brushes, 1075–1076
monolithic fiber brush, 1076
occasional interruptions, 1072–1073
oil-lubricated sleeve bearing, 1068–1069
optimum brush, 1085
over-commutation, 1082
oxidation, 1051
particle transfer, 1048
residual current, arc duration and, 1061–1063
single contact, rupture of, 1042–1043
steady-state super temperatures, 1065
temperature effects, 1064–1068
transfer and growth model, 1048
transfer wear model, 1048
transient effects in brush and collector applications, 1067
under-commutation, 1082
vibration, 1048
wear resistance, 1134
Sliding motion, small-amplitude, 742
Sliding speed, effects of, 1166–1169
Sliding wear, 415
delamination and subsurface wear, 427–428
electroless gold plating, 423
electroless nickel plating, 423
fretting, 441–448, See also Fretting
of multifiber brushes, 1156–1170
rider wear, 421
tin and tin-lead alloys, 437–439
underplate and substrate, effect of, 428–431
underplate hardness, relationship of wear to, 431–435
unlubricated adhesive wear, 432
electrographic wear indexes from, 429
unlubricated palladium-palladium contacts, 487
wiping contaminant from contact surfaces, 417–418
Slip events, 1100
composite materials for, 1133
electrical model of, 1141
noise, 1109
as transmission lines, 1139–1140
SMA, See Shape-memory alloy
SME, See Shape-memory effect
Soft ductile metals, 419
Softening voltage, 95–96, 1198
Soft magnetic nickel-iron alloys, 246
Soft sticking, 695
Solid lubricants, 504
composite materials for brushes, 1133
Solid state vs. mechanical switches, high frequency circuits, 609–610
Solid 1st state of matter, 554
Spark, 563
Sparkless commutation, 1086
Special brush holder, 1049, 1050
Speedometer switch, 700
Splitter plates, 603, 788, 801, 802, 824
calculation in thin film, 18–20, 709
remarks on calculation of, 20–22
Spring materials, 526, 1205–1206
Square a-spots, spreading resistance of, 10, 11
Stannic oxide (SnO2), 49
Stannous oxide (SnO), 49
Starter motors, automotive, 1088–1089
Static vs. dynamic contact resistance, See Contact resistance
Static friction coefficient, 489
Static mechanical contact, 1095
Stationary anode spots, 608
Statistical time lag, 571
Steady state temperature distribution, closed contacts, 65, 103–104
STM, See Scanning Tunneling Microscope Streak technique, 996
Stress corrosion cracking (SCC), 124–125
electric current effect on, 302–305
static vs. dynamic, 267
Strikes effect on porosity, 530–531
Stylus profilometer, 757
Substrate
effect of underplate and, 428–431
role of underplate and, 467–468
roughness, porosity and, 529–531
Sulfur dioxide (SO2), 117, 131, 163
Superficial initial oxides, mechanical disruption of, 452
Supplementary organic lubricant, 485
Surface deactivation treatment, 690–691
Surface film effects, 141
on constriction and contact resistance, 18
electrically insulating/weakly conducting, 45–47
Surface films, 393–396, 1107, 1170–1173
Surface forces apparatus (SFA), 1157
Surface micro-roughness, 4
Surface penetration, 1047
Surface pressure, 1045
Surface profile
using non-contact laser probe, 757
Switch arc motion control, 998–999
Switches, low current, 733–781
design, 779
change-over configuration, 735–737
coefficient of restitution, 749–751
contact bounce, 779
contact welding on make, 774–775
“hair spring” configuration, 736, 737
hand-operated rocker-switch mechanism, 744–746
impact mechanics, 748–749, 752
impact times, 755
lever, 737
low-current alternating current arcs, 768–770
low-current direct current arcs, 761–765
low current, electrical characteristics on closing, 773–774
make-down configurations, 735, 736
make operation, 747–748, 780–781
make-up configurations, 735, 736
membrane switches, 739
normal operation, rocker-switch, mechanism, 744
on-off configuration, 735, 736
opening characteristics, switching devices, 746–747
pivoting mechanism, impact mechanics for, 751–752
remote control switches, 794
rocker-switch mechanism, 734–737
rotary switches, 738
slide switches, 738
snap action, 735
soft action, rocker type, 744
static design parameters, 741–743
switching devices, 739
thermostatic control switch, 740–741
velocity influence, during first bounce, 777–778, See also Point-on-wave (POW)
Switching of d.c. circuits, See Arc interruption
Synthetic graphites, 1083
T
Tabor equation, 1174
Tangential brushes, 1180
Tangential fiber brush, 1154–1156
Tangential forces, 1100
observation and analysis of, 117–118, 129, 140–143
reaction, 114
Teflon-thickened greases, 503–504
TEM, See Transmission electron microscopy
Temperature-dependent ceramics/polymers, 821
Temperature-dependent electrical resistivity, voltage-temperature relation with, 60–62
Temperature distribution in a-spot vicinity, 63–64
plane of maximum value, 100–104
Temperature vs. voltage, in asymmetric contact, 64, 1066
Ten-finger parallel contacts, 649
Tensile strength, hardness and, 651
cold working, 651
Terminal position assurance (TPA), 383
Testing switching contacts
AC vs. DC, 978
bounce, 980
contact resistance, 982
erosion, 981
load type, 974
motion, 996
welding, 989
Test systems, mixed-gas environments, 169
T–F electron emission, See Electron emission
Thermal conductivity, 1198
constants, 68
of metals and Wiedemann–Franz Law, 96–100
voltage-temperature relation with, 60–62
Thermal diffusion in platings, 532–539
Thermal expansion
Thermal-magnetic (T-M) breaker, 850–851
power balance equations, 604
Thermionic reignition, 603
Thermoelastic ratcheting effect in bolted aluminum joints, 266
Thin contaminant films, electrically conducting layers and, 23–28
Three dimensional (3–D) surface measurement systems, 757–758
Three-gas tests, 168
Tin
corrosion mechanisms, 152
oxide and resistivity, 54, 141
plating thickness, 521
as terminal coating material, 393
and tin alloys, 280–282, 437–439
Tin and tin–lead alloy systems, 466–467
Tin-base coatings vs. tin-base surfaces, 453–456
Tin-based contacts, degradation of, 439
Tin contacts, classical electrical contact theory in, 88–89
Tin–copper interfaces, intermetallic growth in, 40–41
Tin–lead-coated checkerboard surface, 479
Tin oxide, growth rate and electrical resistivity, 49–50
Tin-plated contact regions, surface morphology of, 454–455
Tin-plated copper contacts, surface morphology of, 466–467
Tin–tin contacts, 134
degradation of, 478
T-M breaker, See Thermal-magnetic breaker
Torch brazing, 967
nut factor, 319
Townsend avalanche, 561
Townsend breakdown, 563
TPA, See Terminal position assurance
Transient recovery voltage (TRV), 598, 798, 831
Transients, power quality issues, 347
Transmission electron microscopy, (TEM), 1111
Transverse magnetic field, 596
Transverse magneto resistance, 240
Transverse rupture strength (TRS), 916
TRS, See Transverse rupture strength
TRV, See Transient recovery voltage
Tungsten, 245
Tungsten contacts, 689, 718, 936–937
Tungsten–silver contacts, 659–665, 908–928
Tungsten–silver microstructure, 913
Tunnel resistance, 713
Turbo-generator brushes, 1090
Two-body abrasion, 424, 427, 433
Two-body abrasive wear, electrographic wear, indexes from, 430
Type I (Unstable) contact resistance, behavior, 449–452
Type II (Intermediate) contact resistance behavior, 449–452
Type III (Stable) contact resistance behavior, 449–452
U
Underwriters Laboratory, (UL), 327, 794, 806
Ultrasonic cleaning, 225
Underplate
nickel, See Nickel underplate
reduction in chemical reactivity of finishes by, 531–532
Unintentional contamination, 1117–1119
Unmated exposures, mated vs., 172–174
US type miniature circuit-breaker, 815–816
V
anode spot, 594
axial magnetic field, 596–597, 832
columnar, 595
interruption in alternating circuits, 607–608
modes, 595
and short-gap breakdown, 566–569
transverse magnetic field, 596, 832
Vacuum breakdown, 566–569, 602
critical fields, 568
electron emission, 566
enhancement factor, 568
Vacuum circuit breakers, 831
Vacuum interrupter contact materials
other suggestions, 836
requirements, 835
tungsten–copper/tungsten carbide–silver, 836, 935–936, 1210
Vacuum interrupters
principle/applications, 828–829
recovery and influence of design, 607, 831–839
simulation of arcs in, 839–840
Van der Waals force, 1119
Vapor deposition, 393
Vapor phase corrosion inhibitors (VCIs), 180
Verband der Elektrotechnik (VDE), 794
Velocity effects
opening and closing, 980
switches, make operation, 752
Velocity factor (VF), 871
Velocity strengthening, 1102
Vertical free burning arc, 580
VF, See Velocity factor
Vibration, corrosion effect, 180
Vickers hardness (VH), 1196
Visual inspection of corrosion, 129
Voltage characteristics of molten metal bridge, 573
Voltage–current characteristics
function of contact gap, 591
for gas breakdown, 570
of separated contacts, 569–570
Voltage regulator, 1088
Voltage–temperature relation, 5, 58–60, 96, 572, 723
deviation in assymetric contact, 64–65
with temperature-dependent electrical
resistivity and thermal conductivity, 60–62
validity of, 84
W
Water-sealing products, 343
Water vapor, 1125, See also Humidity
in saturated air, 1209
Weakly conducting films, 45–47
Wear, 415, 1047–1048, 1071, See also Sliding wear; Fretting
delamination and subsurface wear, 427–428
delamination mechanism of, 271, 481
rider wear, 421
stages in, 438
tin and tin–lead alloys, 437–439
underplate and substrate, 428–431
to underplate hardness, relationship of, 431–435
unlubricated adhesive wear, 432
electrographic wear indexes from, 429
unlubricated palladium–palladium contacts, 487
Wear characteristics, 1137–1138
Wear resistance, 1134
Wedge-flow mechanism, 437
Weibull distribution, 986
Weight gain measurements of corrosion, 129
Welded contact assembly designs
friction welding, 966
percussion welding, 965
resistance welding, See Resistance welding
special welding methods, 965–966
ultrasonic welding of, 965–966
as contacts open, 657
dynamic welding, 654–657, 902–903
silver metal oxide materials, 904
static welding resistance, 902
switching contacts, See Contacts switching
Wexler’s formula, 1111
Whiskers
silver, 542
White plague, 132
Wiedemann–Franz law, 62–63, 96–100, 477
electrical resistivity and thermal conductivity, 96–100
Wipe cleaning motion, 417
contacts, sliding and, 482–486
motion, 742
Wire connectors, 236
Wire-welding, 963
Wire–wire twist terminal, 384–385
Wire-wound potentiometers, 1133
Work hardening
first bounce, 777
switches, make operation, 750
Worst-case office air condition, 145
Wound field magnet motor, 1086, 1088
Wrought noble contact metals, 426
X
XES, See X-ray energy spectroscopy
XPS, See X-ray photoelectron spectroscopy
X-ray diffraction analysis of fretting debris, 280
X-ray energy spectroscopy (XES), 188
X-ray photoelectron spectroscopy (XPS), 129, 272, 693, 695
Y
Yielding, See Deformation
Yield stress vs. hardness, 250, 651
Young’s modulus, 681
of elasticity, 1045
Z
ZCA, See Zone of closest approach
Zero-insertion-force (ZIF), 383
ZOI, See Zone of influence
Zone of closest approach (ZCA), 1098
Zone of influence (ZOI), 1120
Zone selective interlocking (ZSI), 871
3.145.125.51