PLC内有很多的辅助继电器，其线圈与输出继电器一样，由PLC内各软元件的触点驱动。辅助继电器也称中间继电器，它没有向外的任何联系，只供内部编程使用。它的电子常开/常闭触点使用次数不受限制。但是，这些触点不能直接驱动外部负载，外部负载的驱动必须通过输出继电器来实现。如下图中的M300，它只起到一个自锁的功能。在FX2N中普遍途采用M0～M499，共500点辅助继电器，其地址号按十进制编号。辅助继电器中还有一些特殊的辅助继电器，如掉电继电器、保持继电器等，在这里就不一一介绍了。
在PLC内的定时器是根据时钟脉冲的累积形式，当所计时间达到设定值时，其输出触点动作，时钟脉冲有1ms、10ms、100ms。定时器可以用用户程序存储器内的常数K作为设定值，也可以用数据寄存器（D）的内容作为设定值。在后一种情况下，一般使用有掉电保护功能的数据寄存器。即使如此，若备用电池电压降低时，定时器或计数器往往会发生误动作。
AKER WADE TWINMAX 5002 INDUSTRIAL BATTERY CHARGER 500A
TECO WESTINGHOUSE 450HP ELECTRICAL MOTOR 2300V 1187RPM
NACHI-FUJIKOSHI CORP RBX1400 SERVO AMPLIFIER ROBOT AMP
FIRST LC-1 1/2 VARIABLE SPEED VERTICAL MILLING MACHINE
SURE FLAME S2200 D CONSTRUCTION HEATER 2,250,000 BTU/HR
VALMET AUTOMATION JETMATIC MINI ACTUATOR STAINLESS SS
RELIANCE ELECTRIC 803456-3T 240VD 25A FIELD POWER MODUL
GE 0471L0280 G001/RR FAULT MONITOR INTERFACE PC BOARD
ALLEN BRADLEY CENTERLINE 2300V 4000V MOTOR STARTER HVC
NEW ALLEN BRADLEY REGULATOR SDK3000 PLUS S3DK2004
ALLEN BRADLEY CENTERLINE 2300V 4000V STARTER 1502 HVC
ALLEN-BRADLEY SCR STACK ASSEMBLY WITH THERMISTOR 80157
TECO WESTINGHOUSE 300HP ELECTRICAL MOTOR 2300V 1785RPM
ABB ROBOTICS MODEL IRB 6400 ROBOT USED IRB 6400
SUTORBILT ROTARTY POSITIVE BLOWER CAT1833V MOD GFNEECA
ABB SAFUB 800F500 AC DRIVE CAPACITOR ASSEMBLY 500V
TURNER DESIGNS TD-4100 OIL IN WATER DETECTOR METER 2GPM
TECO WESTINGHOUSE 250HP MOTOR 1180RPM 4160V AEHA-TK000
RELIANCE ELECTRIC 15FR4042 FLEXPAK 7.5/15HP DC DRIVE
NEW GENERAL ELECTRIC 0471L0217G001 CIRCUIT BOARD
NEW GENERAL ELECTRIC 0471L0164G002 REED RELAY CARD
FOXBORO A092678 DIAPHRAGM 6″ EXTENSION FOR 13FEA D/P
ROSEMOUNT INTELLIGENT FIELD TRANSMITTER IFT3000 115V 5A
RELIANCE ELECTRIC 800123-T TACHOMETER RESOLVER 800123T
HONEYWELL FIELD CONTROLLER FC-R FLONPB-N-04 PMD 24V DC
FALK MODEL 129Y1-8 RATIO 2.961 ENCLOSED GEAR BOX DRIVE
ABB YPP 110A & YPK 112A DC DRIVE APPLICATION CONROLLER
VALMET IQ CALIPER FIX HEAD SPARE PART KIT COIL ASSEMBLY
NEW RENOLD WORM GEAR REDUCER MODEL WM8H10 RATIO 10:1
GOULDS JC 3J PUMP FLANGE SUCTION COVER SIZE 18-1/2″OD
ALLIS CHALMERS PUMP COVER STUFFING BOX 6-3/4″ID 23″OD
ZELLWEGER TXPRO-2 POLYMETRON ANALYTICS TRANSMITTER 200R
FISHER ROSEMOUNT CL6003 IAC CL6603 MPU ROM 46A6607X0CR
