描述
共享型以太网或半双工以太网的媒体访问是由载波侦听多路访问/碰撞检测(CSMA/CD)确定的。在半双工的通讯方式下,发送和接收不能同时进行,否则数据会发生碰撞。站点发送前,首先要看是否有空闲的信道。发送时,站点还会在一段时间内收听,确保在这一时间内没有其它站点在进行同步传送,最终本站发送成功。反之,发生碰撞,源站点发送阻塞信号加强碰撞。竞争站点延迟后(延迟时间由算法确定,是随机的)重试。在这种机制下,所有站点和所有集线器都必须在同一碰撞域内。对工业以太网来说,10Mbps和100Mbps是最常用的。在10Mbps,全部采用双绞线的以太网网络中,与距离有关的概念有两个,即网段(Segment)和网络范围(Network Diameter)。前者指连接两个设备(集线器、交换机或主机)的距离,后者指网络中两个最远端设备之间的距离。不管是10Mbps或100Mbps的网络,网段的最远距离不能超过100米。考虑网络延伸,最有用的规则就是5-4-3规则(仅仅针对10Mbps中继器)。规则的内容如下:一个网络最多有五个网段,四个中继器,不多于三个的混合网段。混合网段指的是同轴总线网段(已淘汰)。由于双绞线网段的最远距离是100米,最大网络(网络范围)就是500米。
主营:世界知名品牌的PLC、DCS系统备件模块
①Allen-Bradley(美国AB)系列产品》
②Schneider(施耐德电气)系列产品》
③General electric(通用电气)系列产品》
④Westinghouse(美国西屋)系列产品》
⑤SIEMENS(西门子系列产品)》
⑥销售ABB Robots.FANUC Robots、YASKAWA Robots、KUKA Robots、Mitsubishi Robots、OTC Robots、PanasonicRobots、MOTOMAN Robots。
⑦estinghouse(西屋):OVATION系统、WDPF系统、MAX1000系统备件。
⑧Invensys Foxboro(福克斯波罗):I/A Series系统,FBM(现场输入/输出模块)
顺序控制、梯形逻辑控制、事故追忆处理、数模转换、输入/输出信号处理、数
据通信及处理等。Invensys Triconex:冗余容错控制系统、基于三重模件冗余(TMR)
结构的zui现代化的容错控制器。
⑨Siemens(西门子):Siemens MOORE,Siemens Simatic C1,Siemens数控系统等。
⑩Bosch Rexroth(博世力士乐):Indramat,I/O模块,PLC控制器,驱动模块等。
◆Motorola(摩托罗拉):MVME 162、MVME 167、MVME1772、MVME177等系列。
STAINLESS STEEL HOPPER 60 GALLON HEAT EXCHANGER&PUMP
CONDENSER,MICRO BREWERY,BIODIESEL,AIR DRYER,
EMERSON MOTOR CONTROL T-60 OPERATOR INTERFACE TERMINAL
CAMCO 601RDM4H24-330 ROTARY RDM INDEXER BALDOR 90V DC
FANUC A06B-0143-B075 AC SERVO MOTOR MODEL a12/3000
FANUC A06B-0127-B675 MODEL a6/2000 SERVO MOTOR#7000RS
ABB SIEMENS 1FK6083-6AZ21-9ZZ9-Z SERVO MOTOR 150 KG
OMRON ZFV-CA45 COLOR SENSOR W/SFV-SC150 SENSEHEAD
THERMAL DYNAMICS PAK MASTER 50 PLASMA CUTTING SYSTEM
YOKOGAWA DD SERVO ACTUATOR DR1300A60 MOTOR#94RA0551C
MATTHEWS PRO-POINT P31 TOUCH SCREEN INTERFACE
MMC-SD-1.0-230 GIDDINGS&LEWIS CONTROL MODULE
SP1204 CONTROL TECHNIQUES UNIDRIVE
YOKOGAWA DD SERVO ACTUATOR DR1030B60 MOTOR#94RB39830
KENSOL MARKING EQUIPMENT HEAT FOIL PRESS HEAT STAMP
FANUC A06B-0127-B677 MODEL a6/2000 SERVO MOTOR#7000
FANUC A06B-0127-B575#7000 SERVO MOTOR a6/2000
FANUC A06B-0127-B577#7008 SERVO MOTOR a6/2000 REFUR.
BANNER A-GAGE EZ-ARRAY MEASURING SENSORS W/SOFTWARE
YT213001-BC/2 FANUC AXIS DRIVE UNIT NEW
FANUC A06B-0127-B675 MODEL a6/2000 SERVO MOTOR#7000
GRACO FIRE BALL SERIES B09D GREASE PUMP FOR 20 GAL DRUM
FLUID AUTOMATION INC.PNEUMATIC GREASE COMPRESSOR
GIDDINGS&LEWIS MMC 2-AXIS ANALOG UNIT W/MMC ETHERNET
OMRON GPC03 GRAPHIC PROGRAMMING CONSOLE,W/ACCESSORIES
HOFFMAN 2 DOOR ENCLOSURE W/ALLEN BRADLEY 60 AMP SWITCH
11800-PR01D STAR AUTOMATION SEQUENCE BOARD NEW
UNITED SILICONE UNI-PRINTER UP 300 PAD PRINTER W/TOOLS
YOKOGAWA PARKER COMPUMOTOR DYNASERV SR1030B62 DD SERVO
YOKOGAWA DD SERVO ACTUATOR DR1300A60 MOTOR#94RA0551C
FANUC A16B-2200-0842 MAIN CPU PCB BOARD
1551471 MTI-1 BRIDGEPORT INTERFACE CARD NEW
3169-108 EATON/LEBOW LOAD CELL NEW
A16B-1210-0970/04B FANUC AXIS CONTROL BOARD NEW
10MAIO-16 DAYTRONIC BOARD LOGIC I/O BOARD NEW
LG10A65PIQ BANNER PHOTOELECTRIC LASER W/CABLE MQDC-830
STANLEY VIDMAR 4 DRAWER TOOL CABINET BALL BEARING SLIDE
GE FANUC AFE TECHNOLOGIES CONTROL PANEL IC752DFT000A
YOKOGAWA COMPUMOTOR 500 INDEXER W/CABLES&MANUALS
YOKOGAWA DARWIN DATA ACQUISITION UNIT DA100-D1-1M,S10
WEIGH-TRONIX 3275 CHECKWEIGHER DIGITAL SCALE 6 LB
FANUC VELOCITY CONTROL UNIT A06B-6050-H304
RCC48 GE CONTROLLER CARD
TAMAGAWA FA-CODER ENCODER TS5850 N60,5K-1X-3-8-108
GE FANUC 90-30 CPU PROCESSOR MODULE PN#IC693CPU331-CD
SIEMENS MICROMASTER 440 VFD 1.50 KW 6SE6440-2UD21-5AA1
YOKOGAWA PARKER COMPUMOTOR DYNASERV SR1015B62 DD SERVO
A20B-1000-0560/02B FANUC BOARD NEW
YOKOGAWA DARWIN DCV/TC/RTD INPUT MODULE DU100-11 S1
060-1430-06 HONEYWELL LOAD CELL SENSOR NEW IN BOX
9504-50 ALLEGRO VENTILATION BLOWER
REXROTH INDRAMAT COMMUNICATIONS MODULE RMK12.2-IBS-BKL
LSS-120/208-3Y LEA INTERNATIONAL SURGE SUPPRESSION NEW
ALLEN BRADLEY 1756-IF8/A ANALOG INPUT CONTROL LOGIX
MOTOMAN YASKAWA MRC JANCD-MSL02 MRC CARD NEW
ITW VORTEC CABINET COOLER MODEL 721 VENTURI COOLER NEW
A16B-1210-0940 FANUC SUB MEMORY BOARD NEW
C500-CT001 OMRON COUNTER CONTROLLER NEW
C500-CT001 OMRON COUNTER CONTROLLER NEW
TOKIMEC ELECTRONIC CONTROLLER MODEL EC-Y-S-1A-25 NEW
STNM-DR-040B(U)SANYO NUTRUNNER SERVO DRIVER
437D493 GE AUXILLARY MOTHER BOARD LIGHTING CONTROL
6454-5MO MEDAR FIRING BOARD NEW
75B49 STRUTHERS-DUNN OUTPUT MODULE NEW IN BOX
EATON LEBOW LOAD CELL 3397-200 W/OVERLOAD PROTECTOR NEW
QEL CTS-M5 TOXIC GAS TRANSMITTER/SENSOR MONITOR NEW
SENSOTEC IN-LINE AMPLIFIER PART#060-6827-02
BANNER MINI-SCREEN MSCA-1 LIGHT CURTAIN CONTROLLER
JANCD-MRY01 YASKAWA MOTOMAN PCB MOTION CONTROL BOARD
JANCD-MCP02-1 REV C YASKAWA CNC MOVEMENT CONTROL BOARD
JANCD-MIF05 YASKAWA YASNAC PC BOARD REV.B USED
JANCD-MEW02 REV B YASKAWA PC BOARD USED 1 AVAILABLE
JANCD-MCP01 YASKAWA PC BOARD USED
437D491 GE MOTHER BOARD LIGHTING CONTROL
TAMAGAWA SEIKI TS5858 N 5/5K-1X-ET5-3-9.52-0 FA-CODER
503-17132-00 GIDDINGS&LEWIS PIC TURBO PROCESSOR
UM840 NACHI BOARD NEW
MKS 0248A-01000SV GENERAL PURPOSE FLOW CONTROL VALVE
57701-481 DURANT DIGITAL BIDIRECTIONAL COUNTER NEW