描述
在继电器控制线路中，当电源接通时，线路中各继电器都处于受制约状态，该合的合，该断的断。而在PLC的梯形图中，各“软继电器”都处于周期性循环扫描接通中，从客观上看，每个“软继电器”受条件制约，接通时间是短暂的。也就是说继电器在控制的工作方式是并行的，而PLC的工作方式是串行的。
Vintage Tascam 38 8-Channel Reel-to-Reel Track Recorder
Tascam CD-RW900SL Slot Loading CD Recorder
TASCAM CD-RW900SL CD RECORDER
USED TASCAM IFAN24 AD/DA MODULE
Tascam CC-222SL MKII Slot-Loaded CDRW Cassette Deck
Free Shipping on ALL! music123 Orders!
TASCAM CD-01U CD01U PRO RACKMOUNT CD PLAYER NEW
One-day shipping available
Tascam CD-01U PRO Professional Rackmount CD MP3 Player
Tascam BB1000CD Portable CD/SD Recorder
Tascam RC2424-DEMO Remote Control for MX2424
Tascam CDA750 CD Player/Cass Recorder FREE SHIPPING
Expedited shipping available
NEW TASCAM CD-01U PRO Rack mount CD player CD 01U CD01U
