SNAP-SCM-485 SNAP-SCM-485
在總線兩端連接有端結(jié)器(或終端匹配器)，主要與總線進(jìn)行阻抗匹配，限度吸收傳送端部的能量，避免信號(hào)反射回總線產(chǎn)生不必要的干擾。
總線結(jié)構(gòu)是使用同一媒體或電纜連接所有端用戶的一種方式，也就是說，連接端用戶的物理媒體由所有設(shè)備共享，各工作站地位平等，無中央結(jié)點(diǎn)控制，公用總線上的信息多以基帶形式串行傳遞，其傳遞方向總是從發(fā)送信息的結(jié)點(diǎn)開始向兩端擴(kuò)散，如同廣播電臺(tái)發(fā)射的信息一樣，因此又稱廣播式計(jì)算機(jī)網(wǎng)絡(luò)。各結(jié)點(diǎn)在接受信息時(shí)都進(jìn)行地址檢查，看是否與自己的工作站地址相符，相符則接收網(wǎng)上的信息。
使用這種結(jié)構(gòu)必須解決的一個(gè)問題是確保端用戶使用媒體發(fā)送數(shù)據(jù)時(shí)不能出現(xiàn)沖突。在點(diǎn)到點(diǎn)鏈路配置時(shí)，這是相當(dāng)簡單的。如果這條鏈路是半雙工操作，只需使用很簡單的機(jī)制便可保證兩個(gè)端用戶輪流工作。在一點(diǎn)到多點(diǎn)方式中，對線路的訪問依靠控制端的探詢來確定。然而，在LAN環(huán)境下，由于所有數(shù)據(jù)站都是平等的，不能采取上述機(jī)制。對此，研究了一種在總線共享型網(wǎng)絡(luò)使用的媒體訪問方法：帶有碰撞檢測的載波偵聽多路訪問，英文縮寫成CSMA/CD。
這種結(jié)構(gòu)具有費(fèi)用低、數(shù)據(jù)端用戶入網(wǎng)靈活、站點(diǎn)或某個(gè)端用戶失效不影響其它站點(diǎn)或端用戶通信的優(yōu)點(diǎn)。缺點(diǎn)是一次僅能一個(gè)端用戶發(fā)送數(shù)據(jù)，其它端用戶必須等待到獲得發(fā)送權(quán)；媒體訪問獲取機(jī)制較復(fù)雜；維護(hù)難，分支結(jié)點(diǎn)故障查找難。盡管有上述一些缺點(diǎn)，但由于布線要求簡單，擴(kuò)充容易，端用戶失效、增刪不影響全網(wǎng)工作，所以是LAN技術(shù)中使用***普遍的一種。
OPTO-22 SNAP-M64 Snap I/O Rack NIB
NEW OPTO-22 SNAP-M64 BASE BOARD
OPTO 22 RACK, OPTO SNAP 4 MODULE SNAP-B4M
OPTO 22 SNAP I/O Rack B Series SNAP-M64 16 Module Rack
OPTO 22 SNAP-B8M NSFP SNAPB8M
Opto 22 Snap Analog Input Unit, # SNAP-AIV, WARRANTY
Opto 22 SNAP-AIRATE 2-Ch 0-25,000 Hz Analog Rate Input Module
OPTO 22 SNAP-M16 USPP SNAPM16
OPTO 22 SNAP-D12M USPP SNAPD12M
OPTO 22 5VDC POWER SUPPLY
OPTO 22 SNAP-AOA-3 SINGLE CHANNEL OUTPUT 4-20MA ***XLNT***
Opto 22 SNAP-B12M SNAP B-Series 12-Module Rack Board
OPTO 22 SNAP-B8MC USPP SNAPB8MC
OPTO 22 SNAP-B8M USPP SNAPB8M
OPTO 22 Part No. SNAP B16MC 16 Slot Module Rack / Base
Opto 22 Snap I/O SNAP-G4DA7
Lot of 6 Opto 22 SNAP-ODC5SNK 4Ch 5-60VDC Output Module
OPTO 22 SNAP-B16MC Module Rack / Base **XLNT**
OPTO 22 SNAP-AIV-72 USPP SNAPAIV72
OPTO 22 SNAP-AIVRMS SNAP 2-Ch 0-250 V RMS AC/DC Analog Input Module
OPTO 22 SNAP-AIV-72H USPP SNAPAIV72H
OPTO 22 Part No. SNAP B12MC 12 Slot Module Rack / Base
New OPTO-22 DC Input Module, SNAP-IDC5
OPTO 22 SNAP-D6MC NSFP SNAPD6MC
OPTO 22 SNAP-B4M USPP SNAPB4M
OPTO 22 SNAP B16M I/O Board with Rack/Base: New In Box
Opto 22 G4REG Brick Power Regulator Logic Controller Module Relay Voltage Snap
Lot of 3 Opto 22 Snap I/O SNAP-G4AD7
OPTO 22 Snap-B8MC + (1) Snap I/O
OPTO 22 SNAP-B16MC Module Rack / Base
OPTO 22 SNAP-B16-M/SNAPB16M 16-SLOT RACK/BASE ***XLNT***
OPTO 22 SNAP-B8MC RACK 8MOD W/EXTRA TERMINAL BLOCK*XLNT
OPTO 22 SNAP-D4MC NSFP SNAPD4MC
OPTO 22 SNAP MODULE RACK, B12MC
Opto 22 SNAP-M32 8-Module rack - New no box
NEW OPTO 22 SNAP-IDC5D I/O MODULE 4 CHANNEL DC INPUT 2.5-28VDC 5VDC LOGIC
Opto 22 SNAP-ODC5SRC
Opto 22 SNAP-IDC5
OPTO 22 SNAP-IDC5D 4 CHANNEL DC INPUT MODULE
Opto 22 Snap I/O SNAP-G4AD5
OPTO 22 12-SLOT SNAP I/O BACKPLANE BOARD SNAPD12M
OPTO 22 SNAP D6M 6-SLOT SNAP RACK ***NIB***
OPTO 22 SNAP-IDC5 SNAPIDC5 Input Module ! NEW !
OPTO 22 SNAP-D6M USPP SNAPD6M
OPTO 22 SNAP-IDC5-SW NSPP SNAPIDC5SW
OPTO 22 SNAP-ODC5SNK NSFP SNAPODC5SNK
Opto 22 Snap I/O SNAP-G4AD3 - NEW
OPTO 22 SNAP-ODC5SNK 4 CHANNEL DC OUTPUT MODULE NEW
OPTO 22 SNAP-ODC5SNK 4 CHANNEL DC OUTPUT MODULE
LOT (2) NEW OPTO 22 I/O DIGITAL MODULES SNAP-ODC5SNK
OPTO 22 SNAP-AOA-3 1Ch 4-20mA Loop Analog Output Module
OPTO 22 SNAP-IDC5-SW USPP SNAPIDC5SW
35108 New In box, Opto 22 SNAP-IDC5 I/O Module 4Ch 10-32Vdc 5Vdc Logic
OPTO 22 SNAP-D4M NSFP SNAPD4M
OPTO 22 SNAP-OAC5 NSFP SNAPOAC5
OPTO 22 SNAP-OAC5-I NSFP SNAPOAC5I
OPTO 22 SNAP-ODC5-I NSFP SNAPODC5I
OPTO 22 SNAP-IAC5 NSFP SNAPIAC5
Opto 22 Snap I/O Module SNAP-IAC5 4 Ch AC Input NEW
Opto 22 Snap Analog SNAP-AIVRMS
NIB OPTO 22 SNAP-OAC5 SNAP I/0 MODULE 4 CHANNEL
OPTO 22 SNAP-B8M
Opto 22 SNAP-0DC5SRC Solid State Relay I/O Module ! NEW !
Opto 22 Model: SNAP-ODC5SRC 4 Channel Snap I/O Module
OPTO 22 SNAP-IAC5A SNAP 4-Ch 180-280 VAC Digital Input Module **NEW**
OPTO 22 SNAP I/O SNAP IDC5 4-Channel DC Input Module
OPTO 22 SNAP I/O SNAP IDC5 - SW - NC 4-Channel Switch Input Dry Contact Module
OPTO 22 SNAP-ODC5SNK USPP SNAPODC5SNK
OPTO 22 SNAP-IDC5 NSPP SNAPIDC5
OPTO 22 SNAP-ODC5-I NSPP SNAPODC5I
OPTO 22 SNAP-IDC5D USPP SNAPIDC5D
OPTO 22 SNAP I/O Part No. SNAP IDC5 4 Channel DC Input
NIB OPTO 22 SNAP-ODC5-I OUTPUT MODULE 4CHANNEL 5-60VDC ISOLATED SNAPODC5I
OPTO 22 SNAP-ODC5-I USPP SNAPODC5I
OPTO 22 SNAP-OAC5 USPP SNAPOAC5
OPTO 22 SNAP-IDC5 USPP SNAPIDC5
OPTO 22 SNAP-IAC5 USPP SNAPIAC5
OPTO 22 SNAP-ODC5R USPP SNAPODC5R
OPTO 22 SNAP-LABEL-4B NSFP SNAPLABEL4B
OPTO 22 SNAP-ODC5R NSFP SNAPODC5R
OPTO 22 SNAP-ODC5SRC USPP SNAPODC5SRC
OPTO 22 SNAP-IDC6FAST 4 CHANNEL HIGH SPEED INPUT MODULE NEW CONDITION IN BOX
Opto 22 Snap I/O (Snap-IDC5) 4 Channel NEW!
NEW OPTO 22 SNAP-ODC5SRC OUTPUT MODULE 4POINT DC DIGITA
OPTO 22 SNAP 1/0 IDC5 4 CHANNEL DC INPUT
OPTO 22 SNAP 1/0 4 CHANNEL AC OUTPUT OAC51
Opto 22 Snap I/O (Snap-ODC5SNK) 4 Channel Output NEW!
OPTO 22 SNAP-IDC5D 4 Channel DC Input **XLNT**
OPTO 22 SNAP I/O SNAP IDC5-SW 4-Channel Switch Input Analog Input Module
OPTO 22 SNAP-ODC5SRC 4 CHANNEL DC OUTPUT 3/4A 5-60V ***NIB***
Opto 22 SNAP-ODC5SRC SNAP 4-Ch 5-60 VDC Digital (Discrete) Output Module
OPTO 22 SNAP-ODC5SRC I/O Digital Input Module Industrial Automation PART REPAIR
OPTO 22 SNAP-IDC5D 4-CHANNEL DC INPUT MODULE ***XLNT***
NEW OPTO 22 SNAP PB16H OR SNAPD4M RACK SNAP D-SERIES
Opto22 SNAP-ODC5SNK SNAP Digital Output Module
Opto22 SNAP-IDC5 SNAP Digital Input Module
Opto 22 SNAP-ODC5SNK 4-Ch 5-60VDC Digital Output Module
OPTO 22 SNAP-ODC5SNK 4-Channel Digital Output Module
Opto 22 Snap I/O (Snap-IDC5) 4 Channel (DC Input) NEW!
OPTO 22 SNAP I/O 4-CHANNEL DC OUTPUT MODULE SNAP-ODC5SRC *NEW*
OPTO 22 1/0 SNAP OAC5-1
OPTO 22 SNAP-ODC5SRC OUTPUT MODULE 4POINT DC DIGITA
OPTO 22 Snap I/0 Module SNAP-IAC5 SNAP IAC5 NEW
OPTO 22 SNAP-IDC5 4 Channel DC Input **XLNT**
OPTO 22 SNAP I/O 4-CHANNEL SOURCE DC OUTPUT MODULE SNAP-ODC5SRC
OPTO 22 SNAP I/O 4-CHANNEL 10-32V DC INPUT MODULE SNAP-IDC5
OPTO 22 SNAP I/O 4-CHANNEL 2.5-28V DC INPUT MODULE SNAP-IDC5D
OPTO 22 SNAP I/O ISOLATED 4-CHANNEL 5-60V DC OUTPUT MODULE SNAP-ODC5-I
Opto-22 Snap I/O 4 Channel DC Input SNAP-IDC5
OPTO 22 SNAP I/O 4-CHANNEL SINK DC OUTPUT MODULE SNAP-ODC5SNK
OPTO 22 SNAP-IDC5 DC INPUT MODULE 4 CHANNEL 10-32VDC ***NIB***
OPTO 22 SNAP-IDC5 MODULE 4 CHANNEL DC INPUT ***XLNT***
NEW OPTO-22 SNAP-IDC5 4-Channel 10-32VAC Compact Digital AC/DC Input Module I/O
Opto 22 snap IAC5
NEW OPTO 22 SNAP-IDC5 INPUT MODULE 4POINT DC DIGITAL
2x OPTO 22 G4 REG 5/24V Brick Power Voltage Regulation Module Regulator SNAP I/O
