模块的外部表现就是它的工作状态的种种显示、种种接口及设定或控制开关。一般讲，模块总要有相应的状态指示灯，如电源显示、运行显示、故障显示等。箱体式PLC的主箱体也有这些显示。它的总线接口，用于接I/O模板或底板，有内存接口，用于安装内存，有外设口，用于接外部设备，有的还有通讯口，用于进行通讯。模块上还有许多设定开关，用以对PLC作设定，如设定起始工作方式、内存区等。
二、I/O模块：
PLC的对外功能，主要是通过各种I/O接口模块与外界联系的，按I/O点数确定模块规格及数量，I/O模块可多可少，但其大数受所能管理的基本配置的能力，即受大的底板或机架槽数限制。I/O模块集成了PLC的I/O电路，其输入暂存器反映输入信号状态，输出点反映输出锁存器状态。
三、电源模块：
83-15-3216 SOLA ELECTRIC POWER SUPPLY NEW IN BOX
501-03410-01/50?2-02947-01 GIDDINGS & LEWIS ENCODER CARD
55700 MAS100 D14/D04 MURR ELEKTRONIK I/O MODULE NEW
ALLEN BRADLEY 1746SC-IA8I ISOLATED INPUT MODULE SER. B
86-24-262 SOLA CUSTOM RECTIFIER POWER SUPPLY NEW IN BOX
137693 MILLER VOLTAGE BOARD NEW IN BOX
SQUARE D COMBINATION MOTOR CONTROLLER W/DISCONNECT
PC-1984-120 MODICON PROCESSOR MODULE 4K MEMORY
MAQ1-00300-000-?5-00 BARBER COLMAN TEMPERATURE CONTROL
C500-CT001, 3G2A5-CT001 OMRON COUNTER CONTROLLER
FC3A-N16B1 IDEC OPEN NET CONTROLLER NEW IN BOX
473-0-0336 ROBOTRON FIRING BOARD
750-556 WAGO 2CH OUTPUT MODULE NEW IN BOX
SICK WS12-2D430 PHOTOELECTRIC EMITTER NEW WARRANTY
C500-ID213, 3G2A5-ID213 OMRON INPUT UNIT
RAPID AIR 69100033 REV. D CONTROL BOARD NEW
RAPID AIR 69100033 REV. D CONTROL BOARD NEW
RAPID AIR 69100035 PWB REV. B CONTROL BOARD NEW?
NORDSON 4 CHANNEL HOSE & GUN TEMPERATURE CONTROL?
8210G095 ASCO RED HAT VALVE NEW IN BOX
MICROSWITCH EXPLOSION PROOF SNAP SWITCH 14CX1 9116 NEW
D2S-A150SS BARKSDALE DIAPHRAGM SWITCH NEW
LIVINGSTON WELDWISE 2400 THE POD RESISTANCE WELD MODULE
IC610MDL180A GE/FANUC RELAY OUTPUT MODULE NEW IN BOX
D3-16TD1-1 PLC DIRECT OUTPUT CARD NEW IN BOX
501-03438-00 P#502-02959-00 GIDDINGS&LEWIS AC INPUT BD
WILLIAMSON FIBERVIEW 1100 HIGH TEMPERATURE SENSOR?
FEDERAL PACIFIC ELECTRIC BUSWAY UNIT 60AMP
652-8-3000 ATC-TENOR TIMER
BARKSDALE MODEL#0428-030 USD7 PRESSURE TRANSDUCER NEW
SIEMENS SIMATIC ANALOG INPUT 6ES7 134-4FB01-0AB0 NEW
176B8013 DANFOSS ELECTRONIC DRIVE
PHOTOCRAFT INC. INCREMENTAL ENCODER PN# RH-4AJ/24P ?NEW
RAYTEK RAYIT1SFS CONTROL BOARD
FANUC A03B-0807-C160 MODULE NEW
HYDE PARK SUPERPROX SM650-700-00AA NEW
C500-DA002, 3G2Q5-DA002 OMRON D/A UNIT NEW IN BOX
060-3590-06 SENSOTEC DLA LINEAR TRANSDUCER
OMRON H7CR-A COUNTER NEW?
5-760-290-0 PROSYS FREINNUM FS PC BOARD 3 PORTS
1-Z8/50N KRAFTAUFNEHMER FORCE TRANSDUCER NEW IN BOX
FANUC PULSECODER A860-0631-T001, aA64
VICKERS VALVE DGMX2 3 PP BW B 40 EN13 NEW
OMRON C120-ID217 (3G2A6-ID27) INPUT MODULE NEW IN BOX
HELM INSTRUMENT CO. INC. STRAIN GAIN HT400 TRANSDUCER
1794IB10XOB6 ALLEN BRADLEY FLEX I/O MODULE NEW IN BOX
SAS AUTOMATION RPL 6 SENSOR LOGIC BOX AND LOGIC
SAS AUTOMATION RPL 6 SENSOR LOGIC BOX AND LOGIC
NOLATRON SERIES 4470 ANTI-TIEDOWN SWITCH MONITOR NEW
1600-PM3-05/(3)?1652-48-70-USD SCR POWER CONTROLLER
1600-PM2-01/(2)?1652-48-70-USD SCR POWER CONTROLLER
