現(xiàn)場(chǎng)終端單元（FTU）是輸入/輸出模塊的一部分，用于
將所有三個(gè)FIU連接到單個(gè)現(xiàn)場(chǎng)設(shè)備。FTU主要包括
前端信號(hào)調(diào)節(jié)、現(xiàn)場(chǎng)信號(hào)所需的無(wú)源元件
過(guò)壓保護(hù)和EMI/RFI濾波。當(dāng)安裝在受信任的
控制器或擴(kuò)展器機(jī)箱，F(xiàn)TU現(xiàn)場(chǎng)連接器互連至
連接在機(jī)箱后部的輸入/輸出電纜組件。
SmartSlot鏈接通過(guò)從HIU傳遞到現(xiàn)場(chǎng)連接
FTU。這些信號(hào)直接傳輸至輸入/輸出電纜組件并進(jìn)行維護(hù)
與FTU上的輸入/輸出信號(hào)隔離。SmartSlot鏈接是智能的
活動(dòng)和備用模塊之間的連接，以便在
模塊更換。
現(xiàn)場(chǎng)接口單元（FIU）是模塊的一部分，包含
與特定類(lèi)型的現(xiàn)場(chǎng)輸入/輸出接口所需的特定電路
信號(hào)。每個(gè)模塊有三個(gè)FIU，每個(gè)片一個(gè)。對(duì)于TMR 24 Vdc數(shù)字
輸入模塊，F(xiàn)IU包含一個(gè)單獨(dú)的模數(shù)（A/D）轉(zhuǎn)換器
對(duì)于40個(gè)現(xiàn)場(chǎng)輸入中的每一個(gè)。
FIU從HIU接收邏輯隔離電源。金融情報(bào)室提供
針對(duì)
FIU電路。一個(gè)隔離的6.25 Mbit/s串行鏈路將每個(gè)FIU連接到
HIU切片。
FIU還測(cè)量一系列機(jī)載“內(nèi)務(wù)”信號(hào)，以協(xié)助
監(jiān)控模塊的性能和運(yùn)行條件。
這些信號(hào)包括電源電壓、電流消耗、車(chē)載
參考電壓和電路板溫度。The Field Termination Unit (FTU) is the section of the I/O Module that connects all three FIUs to a single field device. The FTU primarily contains passive components necessary for front-end signal conditioning, field signal overvoltage protection, and EMI/RFI filtering. When installed in a Trusted Controller or Expander Chassis, the FTU field connector interconnects to the I/O cable assembly attached at the rear of the Chassis. The SmartSlot link is passed from the HIU to the field connections via the FTU. These signals go directly to the I/O cable assembly and maintain isolation from the I/O signals on the FTU. The SmartSlot link is the intelligent connection between Active and Standby Modules for coordination during Module replacement. The Field Interface Unit (FIU) is the section of the Module that contains the specific circuits necessary to interface to the particular types of field I/O signals. Each Module has three FIUs, one per slice. For the TMR 24 Vdc Digital Input Module, the FIU contains an individual analog to digital (A/D) converter for each of the 40 field inputs. The FIU receives isolated power from the HIU for logic. The FIU provides additional power conditioning for the operational voltages required by the FIU circuitry. An isolated 6.25 Mbit/s serial link connects each FIU to one of the HIU slices. The FIU also measures a range of onboard “housekeeping” signals that assist in monitoring the performance and operating conditions of the Module. These signals include power supply voltages, current consumption, onboard reference voltages and board temperature.