随着电子技术的快速发展，印制电路板广泛应用于各个领域，几乎所有的电子设备中都包含相应的印制电路板。为保证电子设备正常工作，减少相互间的电磁干扰，降低电磁污染对人类及生态环境的不利影响，电磁兼容设计不容忽视。 在印制电路板的设计中，元器件布局和电路连接的布线是关键的两个环节。 布局 布局，是把电路器件放在印制电路板布线区内。布局是否合理不仅影响后面的布线工作，而且对整个电路板的性能也有重要影响。在保证电路功能和性能指标后，要满足工艺性、检测和维修方面的要求，元件应均匀、整齐、紧凑布放在PCB上，尽量减少和缩短各元器件之间的引线和连接，以得到均匀的组装密度。 按电路流程安排各个功能电路单元的位置，输入和输出信号、高电平和低电平部分尽可能不交叉，信号传输路线短。
SQUARE D RJF36160U44A 1600 AMP 600 VOLT 3 POLE CIRCUIT BREAKER (A)
SQUARE D RJF36160U44A CIRCUIT BREAKER 3 POLE 1600 AMP 600 VOLT  
SQUARE D RJF36160U64AE1 1600 AMP 600 VOLT 3 POLE CIRCUIT BREAKER
Square D RKF36120U44A PowerPact RK1200 1200 Amp 3 Pole Circuit Breaker LSIG
Square D RKF36160U44A PowerPact 1600A Breaker  XLT COND  LSIG (W0054)
Square D RKF36250CU41DE1SA 2500 Amp 3 Phase Circuit Breaker
Square D RLF36120U44A PowerPact RL1200 1200 Amp 3 Pole Circuit Breaker
Square D RLF46160CU44AE Circuit Breaker, 1600 Amp, 100 kAIR, 4 Pole,   
SQUARE D S163A USPP S163A
SQUARE D S164A NSFP S164A
SQUARE D S164N NSPP S164N
SQUARE D S174A NSFP S174A
Square D S33595 Full Function Test Set -         Circuit Breaker Test Kit
Square D S33595 Full Function Test Set Version 1.20   EST OS 
Square D S3MOT120AC2 SPRING CHARGING MOTOR 120V SEF SED SEM CIRCUIT BREAKER
Square D S48526 or S48211, 100-130 VAC Spring Charging Motor for NW Masterpact
SQUARE D S7550B0C0B6E0A0A NSFP S7550B0C0B6E0A0A
Square D Safety Switch #H362DSWA Fusible 3PST 60A 600V 3PH Stainless Steel
SQUARE D SAFETY SWITCH DISCONNECT NON FUSIBLE / F  HU367 3 PHASE HEAVY DUTY
SQUARE D SAFLEX BUSWAY CIRCUIT BREAKER SD-75715   SD75715
Square D SB 124IR METERED SWITCHGEAR 120/240 NEMA 3R 400 AMP SERIES E2
Square D Schneider Electric S164B 6.0P Micrologic Trip Unit ~   ~
Square D Schneider Electric S33595 Full Circuit Breaker Function Test kit
Square D Schneider LAL34225MC1021 Circuit Breaker 225 Amp 225a Molded Case  
SQUARE D SCHNEIDER MASTERPACT 2500A BREAKER WC4GGR44R9SXFXXXXX
SQUARE D SCHNEIDER NW 30H 3000AMP LSIG   TAKE OUT
Square D Schneider NW12HF 1200 Amp Masterpact Breaker Switch WL3CCHSSX9SXXXXXXX
Square D Schneider SY/MAX 8055SCP452 450 Processor nib
SQUARE D Schneider Well-Guard 8940SSD4030V02S AC PUMP CONTROL PANEL
SQUARE D SD SD3855 SD-3855 600 AMP 600V BREAKER BUS PLUG TAP  BUSWAY 225 400
SQUARE D SD SD67728 SD-67728 250 AMP 600V BREAKER BUSS BUS PLUG BROKEN STAB
SQUARE D SD SD78417 SD-78417 125 AMP 600V BREAKER BUSS BUS PLUG
Square D SD67446 Bus Plug 400A 3PH 4W Breaker Style -    
Square D SE SED 2500A Breaker 2500A ARP080 LSIG Trip 2000A SED362500LSGES5D4
Square D SE SEF 3000A Electronic Trip Breaker 3000 Amp LIG SEF363000LIGA4 SqD
SQUARE D SED361600LIES1A8 600V 1600 AMP M-L L I INSULATED CASE CIRCUIT BREAKER
SQUARE D SED362000LSGET1A8 NSPP SED362000LSGET1A
SQUARE D SED363000LS 600V 3000 Micro Logic L S I INSULATED CASE CIRCUIT BREAKER
Square D SED363000LSES1A8 3000A SE Breaker SED363000 SED-363000 SED363000LS
Square D SED363000LSGES1A8 3000 SE Breaker SED363000 SED-363000 SED363000LSG
Square D SED363000LSGES1D8 3000 SE Breaker SED363000 SED-363000 SED363000LSG
SQUARE D SED364000LS 600V 4000 Amp INSULATED CASE CIRCUIT BREAKER
SQUARE D SED36800LIES5A8 600 V 800 AMP M.L. L I INSULATED CASE CIRCUIT BREAKER
SQUARE D SED36800LSG 600V 800 AMP M-LOGIC L S I G INSULATED CASE CIRCUIT BREAKER
SQUARE D SEDG30M2, 300 AMP, CIRCUIT BREAKER
Square D SEF 1600 Amp SESFG16 Electronic Trip SE Breaker LSIG S9161600RP
Square d SEF SEF363000LSI 3000 AMP AIR CIRCUIT BREAKER
Square D SEF361600LSES1A4 1600 Amp Circuit Breaker
SQUARE D SEF361600LSS1A8 600V 1600 AMP M-L L S I INSULATED CASE CIRCUIT BREAKER
Square D SEF362000LSET6AB 2000A SEF Electronic Trip Breaker 2000 Amp LSI 600V SE
SQUARE D SEF362000LSG 600V 2000 AMP M-L L S I G INSULATED CASE CIRCUIT BREAKER
Square D SEF363000LI 3000A 3-Pole 600V ARP100 Electronic Trip Circuit Breaker
Square D SEF363000LIA4 3000 Amp Electronic Trip SE Breaker LIA SEF
Square D SEF363000LIS2D8 3000A SEF Electronic Trip Breaker 3000 Amp LI 600V SE
Square D SEFG20 2000 Amp 600 Volt 3 Phase Circuit Breaker
SQUARE D SFD21NG2Y USPP SFD21NG2Y
SQUARE D SHNEIDER 7.5KVA ISOLATION TRANSFORMER CAT#SXM07DA HV 277 LV 120  NIB 
SQUARE D SIZE 3 MOTOR STARTER 8538SEG11V81CF4H20P1TX11
SQUARE D SIZE 3 REDUCED VOLTAGE STARTER CAB CAT#8536SEO1 120VCOIL 100A DISC   
Square D Size 4 Combo Motor Starter, Refurbished
Square D Size 5 Combination Starter  400 Amp Stainless Steel SS 3R 8536 F 
Square D Size 5 Combination Starter  400 Amp Stainless Steel SS 3R 8536 Fuse
Square D Size 5 Combo / Enclosed Starter 8538SGG13
Square D size 5 enclosed starter 8536-SG01 200 hp 110/120 coil Guaranteed 
Square D size 5 motor starter 120V coil 200 hp
SQUARE D SIZE 5 STARTER 8536SGO1V02H10S SERIES B
Square D size 6 , Class 8536 , Type SH0-2
Square D Size 6 Contactor , Class 8502 , Type HO2
Square D Size 7 Auto Reduced Voltage Starter
SQUARE D SIZE SZ 5 motor STARTER COMBO combination 400A 8538 SGG33 B 8536
SQUARE D SIZE SZ 7 REVERSING STARTER 8702 SJO-1 8702 SJO1 8702 SJ0-1
SQUARE D SMSDL NSFP SMSDL
SQUARE D SOILD STATE TRIP CIRCUIT BREAKER 3000 AMP 600V 3 POLE SEF30S1 S930LIT
SQUARE D SOLENARD 4.76KV 1200A DRAW OUT DSE23B
Square D Solid State Trip Circuit Breaker Cat. No. MX36800G Rating 800 Amp 600V
SQUARE D SORGEL 150KVA 3PH TRANSFORMER CAT#150T6HCT HV 480 LV 240
Square D Sorgel 3 Phase 2000 KVA 12470-480Y/277 Volt Dry Transber
Square D Sorgel 3 Phase 2500/3250/4332 KVA 4800-480 Volt Dry Transber
Square D Sorgel 3 Phase Dry Transber 2000/2666 KVA 13200-480Y/277 Volt
Square D Sorgel 3 Phase Dry Transber 2500 KVA 4160-480Y/277 Volt
Square D Sorgel 3 Phase Dry Transber 750 KVA 480-208Y/120 Volt
SQUARE D SORGEL 500 KVA TRANSFORMER 480 HV 208Y/120 LV MODEL 500T68H
Square D Sorgel 500T68H 500 KVA 480 to 208Y/120V 3PH Transber Nema 3R  
Square D Sorgel Dry Transber 750 kVA 12470 480Y/277 Copper Coils 480 3PH 60Hz
Square D Sorgel Watchdog 225kva Transber 480HV 208Y/120LV 225T3HB
Square D SQ D Disconnect Switch 1600A 1600 Amp 500V Thermal-Magnetic Breaker 500
Square D SQ D Disconnect Switch 2000A 2000 Amp 600V Thermal-Magnetic Breaker 500
Square D Sq d FC4IMA24C I-Line Surgelogic Transient Voltage Surge Suppressor  
Square D SQ D MAL36900 Circuit Breaker 900Amp
SQUARE D STARTER ENCLOSURE WITH SIZE 4 STARTER AND 150AMP BREAKER KAL361502
SQUARE D SURELOGIC SURGE PROTECTIVE DEVICE CAT#FC4IMA16 480V 160kA 3PH W/BREAKER
Square D Surgelogic FC4IMA16C I-Line Surge Protective Device 160ka
Square D Surgelogic FC4IMA16C Surge Protective Device
Square D Surgelogic TVS8IMA12P MA8IMA12 TVS3DSPH
Square D SURGELOGIC Voltage Surge Suppressor TVS4EMA16A 160kA 480Y/277V 3PH  
Square D Switchboard Circuit Breaker QED 1200a 480v I-Line Iline Panel
SQUARE D SY/MAX 8010 SFI 510 SER A1 REV 2.01 COMMUNICATION INTERFACE
SQUARE D SY/MAX 8020 SCP401 PROCESSOR
SQUARE D SY/MAX 8020-SCP-424 MODEL 400 PROCESSOR 8020SCP424
SQUARE D SY/MAX 8020-SCP-724 MEMORY MODULE 8020 SMM-710
Square D SY/MAX PLC 8010-SFI-510X INTERFACE BOARD
SQUARE D SY/MAX PROCESSOR MODULE PLC MODEL 400 8020 SCP-444 8020SCP444 SCP444
SQUARE D SY/MAX TYPE SCP632 CLASS 8020 MODEL 600 PROCESSOR REVISION 4.00 5VDC
Square D Symax 650 Processor 8055
SQUARE D SYMAX 8010-SFW-473 8010SFW473 PROGRAMMING SOFTWARE SY/MATE PLUS  
Square D Sz Size 7 Motor Starter Reversing 8736 SJO1S1
Square D Telemecanique 230V ATV66D23M2 25 HP VT 20 HP CT VS Variable Speed Drive
SQUARE D THERMAL-MAGNETIC CIRCUIT BREAKERS 700A, 500A, 200A, (2)100A
Square D Three Phase General Purpose Transber 415Kva -EN415TQ54333R1
Square D Transfomer 150KVA
Square D Transber - 112T76H
SQUARE D TRANSFORMER 150 KVA PRI 480V SEC 208Y/120 3 PH DRY TYPE 150T3H
SQUARE D TRANSFORMER 150 KVA PRI 480V SEC 208Y/120 3 PH DRY TYPE 150T3HBISNL
Square D Transber 1500 / 2000 KVA,  , 1  
Square D Transber 1500/2000 kVA 13200V delta pri 480/277V sec Model 98 TESTED
SQUARE D TRANSFORMER 225 KVA PRI 480V SEC 208Y/120 3 PH DRY TYPE 225T3H47DB
Square D Transber 300T6H-CT #37891
Square D Transber 750 KVA 34.5 KV Y Primary 480v delta secondary oil filled
SQUARE D TRANSFORMER CAT#EE75T3HF 75KVA HV: 480V LV: 208Y/120 3 PHASE    
Square D Transber Disconnect # 9070SK3000A2D1 " "
SQUARE D TRANSIENT VOLTAGE SURGE SUPPRESSOR CAT# TVS1EMA16A 160kA 120/240V
SQUARE D TRANSIENT VOLTAGE SURGE SUPPRESSOR CAT#TVS1EMA24A 240kA 120/240V  NIB 
Square D Triple 800 Amp MCCB Thermal-Magnetic 800Amp i-Line Breaker Main Switch
Square D TVS1EMA12S Transient Voltage Surge Suppressor
Square D TVS2EBA12A Transient Voltage Surge Suppressor
Square D TVS2EMA12A Transient Voltage Surge Suppressor
SQUARE D TVS2EMA12AIC Transient Voltage Surge Suppressor 208Y/120V 3 Ph 4 wire
SQUARE D TVS-2EMA12AISWT NSFP TVS2EMA12AISWT
SQUARE D TVS-2EMA24AIC NSFP TVS2EMA24AIC
SQUARE D TVS4EBA24A NSFP TVS4EBA24A
Square D TVS4EMA16AI 160 KA Peak Surge Protective Device (CIR1749)
SQUARE D TVS4EMA24AC 277/480 TVSS (U) SURGE SUPPRESSOR
Square D Type JGA36250 Circuit Breaker   3 Pole
Square D Type KA26250AC Circuit Breaker   2 Pole
Square D Type MEL436LSGZ1 Circuit Breaker   no plug  
Square D Type PBTB502G Buss DuctTap  225 Amp
SQUARE D TYPE PE 1600 AMP GROUND FAULT CIRCUIT BREAKER.............ZF-301
Square D Type QE3150VH Plug in Main Breaker
Square D type QMB 3P 400A 600V Single Saflex Series E1
Square D type QMB-3640 3P 400A 600V
Square D type QMB366MW 600A 3-Pole 600V Series 1
Square D Type VR Ground and Test Device - Excellent    
SQUARE D V5D3122Y000 4.76KV 1200A DO EO MEDIUM VOLTAGE CIRCUIT BREAKER
Square D V5D7133Y000A 1200A 15kV Vacuum Breaker 1200 A Amp 15 kV Type VR
Square D V5D7233Y000A 2000A 15kV Vacuum Breaker 2000 A Amp 15 kV Type VR
Square D VACARC AC High Voltage Vacuum Circuit Breaker - 4.76KV - 1200Amp
Square D VACARC AC High Voltage Vacuum Circuit Breaker - 4.76KV - 1200Amp
Square D Var-Gard Automatic Power Factor Control - 300KVAR - 480Volt - 600Amp
Square D Var-Gard Automatic Power Factor Control Equipment - 250KVAR 480Volt 3W
SQUARE D VR V5D4133YJ00A 4.76KV 1200A DO EO MEDIUM VOLTAGE CIRCUIT BREAKER
SQUARE D VX5A66D466M2 FNFP VX5A66D466M2
SQUARE D WA4JJR43A9SFBXXCX 600 V 3200 AMP L I G INSULATED CASE CIRCUIT BREAKER
Square D WA8FFR64A3FFBFXXCA MasterPact Low-Voltage Power Circuit Breaker 2000A
Square D WATCHDOG 150 KVA Transber 480 Delta 208Y/120 Volt ONE  GUARANTEE
Square D XBT F024610_XBTF024610_XBT FO2461O_XBTFO2461O with Memory Module PV:02
Square D XBT F024610_XBTF024610_XBT FO2461O_XBTFO2461O with Memory Module PV:06
SQUARE D XBT-F011310 MAGELIS OPERATOR INTERFACE XBTF011310 REPAIRED
SQUARE D XBT-F024610 USPP XBTF024610
SQUARE D XBT-GTW450 NSPP XBTGTW450
SQUARE D XR-IA-DI NSFP XRIADI
SQUARE D XR-IA-DI NSPP XRIADI
Square D YA8KKR63B3LFBFWXCA MasterPact Circuit Breaker 635V 4000A 3P
Square D, NXP361000, 600V, 1000 Amp, Circuit Breaker
Square D, Omegapak, AC Drive, Class 8803, Type P00CO4N
SQUARE D,26039581-003,TYPE IPaCS,HEAVY DUTY TRANSFORMER
SQUARE D,DS BREAKER TEST KIT MODEL 2537-3 WESTINGHOUSE, CUTLER HAMMER AMPTECTOR
Square D,I Line Panelboard complete,1200A Main Lugs only, 86" for breakers,  
Square D/Schneider Electric KI36175 600 Volt 3 Phase SEALED   OFFERS ACCEPTED  
Square D/Schneider Electric LX36125G Circuit Breaker SEALED   OFFERS ACCEPTED  
Square D/Schneider Electric MAP26800 800 Amp braker SEALED   OFFERS ACCEPTED  
Square D/Symax 8010 SFI510 Interface Board for PC, Series A1/Rev 2.01 (NIOP)
Square D/Symax 8030-CRM-232
Square D/Symax 8030-RIM-126
Square D/Symax 8030-SCP-424
Square D/Symax 8030-SCP-444
Square D/Symax/ 8020-SCP-423/8020SCP423/SCP-423/SCP423 OFFERS ACCEPTED  
Square D: 10S9FIS Dry Transber. 1PH, 10KVA, 208V
Square D8538SBW33V81ACFF4H30P42T1 Combination Motor Starter 30A 4/4X
Square D-HVL Load Current Interupter Switch HVL30503
SQUARE I-LINE II BUSWAY CAT# AP2525-G10 SER. 1. ALUM 1200A, 3PH, 4W W/ INT. GRND
SQUARE-D # LX36400-1380 LX36400 400 AMP I-LINE BREAKER  
SQUARE-D # NX361000 CIRCUIT BREAKER
SQUARE-D # NX361200 I-LINE 1200 AMP W / ACCESSORIES
SQUARE-D (8903 SZ0-2) LIGHTING CONTACTOR/STARTER 120VAC COIL 600AMP RATED
SQUARE-D 150 KVA TRANSFORMER HV 480 LV 208Y/120 CAT 33150TD3H UN 
Square-d 1600 amp 480 delta Main Breaker QED panel board 3R enclosed I-Line
SQUARE-D 2000/2667 KVA 4160 480Y/277 VAC TRANSFORMER
SQUARE-D 2500/3333 KVA 13800V 480Y/277 TRANSFORMER
SQUARE-D 3200AMP I-LINE SWITCH BOARD ENCLOSURE PANEL 3-PHASE NEMA-1 W/ BREAKERS
SquareD 40 HP VFD with SOFT START BYPASS ths 40975
SQUARE-D 500 KVA 480 208Y/120 VAC 500T68HIS TRANSFORMER
SquareD 600V 1200A Breaker (PGL36120)
SQUARE-D AUTO TRANSFORMER REDUCED VOLTAGE 400HP STARTER
SQUARE-D CLASS 8536 SPIN TOP MOTOR STARTER 25HP 200V TYPE-SER3 BREAKER
SQUARED D AIR BREAKER DS-632 DS632 3200A 3200A AMP AMPTECTOR I-A MODEL LSG
SQUARE-D DS-416 1600A 600V MO POWER CIRCUIT BREAKER W/ DIGITRIP RMS500 LIG
SQUARE-D DS-632 3200A AC POWER CIRCUIT BREAKER LI
SQUARE-D EE500T68H GENERAL PURPOSE TRANSFORMER 500kVA 480V-208Y/120 3PH DRY TYPE
SQUARE-D I-LINE PANEL BOARD MGA 36800 LA 200 QD 200 UN  POWER PACT