plc其研发目的在于取代以继电器为主之顺序控制，亦即使用程序以取代硬件配线，因此只要改变其程序即可改变其控制的顺序，而轻易的达成控制上之不同需求。一般的plc系以继电器控制回路为基础发展而来，并将继电器的接点和线圈予以符号化，当转换成一般的阶梯图或指令之后，即可实现其控制。但如此所完成的控制回路，是基于电路设计者本身之学习，较为主观及直接，一般使用者往往不易理解其流程，亦即程序的可读性较低。
FOXBORO G0108HA Tableau Lecteur Assemblyy
Foxboro IGP20-T20C21C-M1 Gage Pressure Transmitter 0-840in-h2o 12.5-42v-dc
Foxboro IGP20-T22A01F-L1T Gage Pressure Transmitter 0-10in-h2o 12.5-42v-dc
Foxboro 230SZ-G Spec 200 Control Station
FOXBORO IGP10-D20D1F-L1 Spessore Pressione Trasmettitore 0-300psi 12.5-42v-dc
Foxboro 8006a-wcr-p-jgfgz 8000a Serie Magnético Flowtube 6in 150
FOXBORO 873EC-AIXCNZ Electrodeless Conducibilità Analizzatore 120v-ac
Foxboro E69F-B12 Current To Air Converter 4-20ma 3-15psi
FOXBORO IDP10-F22B21F-M1V Fieldbus Différentiel Pression Transmetteur
Foxboro RH926KH 2pos Chassis Module
Foxboro CUSTOM 63U Alarm Unit Process Controller 118v-ac
Foxboro IGP20-T22A01F-L1T Gage Pressure Transmitter 0-10in-h2o 12.5-42v-dc
Foxboro IGP20-T22A21F-M2L1 Gage Pressure Transmitter -5-10in-h2o 12.5-42v-dc
FOXBORO P6986-810A Eckardt Electro-Pneumatic Valvola Posizionatore
FOXBORO N0309PM 2AC-M2 Doppio Controllo Porta Carta Modulo
FOXBORO KIT-C-E27-A-C Karte Field Umbausatz
Foxboro IDP10-F22B21F-M1V Fieldbus Differential Pressure Transmitter 0-200in-h2o
FOXBORO N-823DP-H3S1SH2 Differential Druck Sender 0-1016cm-h2o
Foxboro 9306A-SIBA-THJ-GK 9300a Series Magnetic Flowtube 6in 150 285psi