The MTL Simplex FISCO power supplies are fieldbus repeater isolators that repeat the fieldbus signal from a safe area, Zone 2 fieldbus to an intrinsically safe fieldbus for connection to devices in Zone 1. The 9121-IS provides up to 120mA, typically powering up to eight 15mA field devices in Gas Group IIC. The 9122-IS provides up to 256mA, typically powering up to sixteen 15mA field devices in Gas Group IIB.
In a FISCO fieldbus network, the entire field circuit, including the trunk and all spurs, is intrinsically safe. The fieldbus power supply includes an intrinsic safety barrier, and provides conditioned power to the fieldbus segment in the hazardous area. The fieldbus instruments together with the power supply and any associated wiring components must be certified as intrinsic safety apparatus and must comply with FISCO requirements. The field instruments may be located in a Zone 0 or 1, IIC or IIB hazardous area, depending on the certification of the individual components.
FISCO enjoys the benefits of any intrinsically safe instrumentation circuit. These advantages include the ability to live-work in the hazardous area without "gas clearance", and, for example, to add or remove a fieldbus instrument while the bus is energized in the presence of a flammable atmosphere. This is critical for Foundation fieldbus installations because field instruments need to be connected to a live network to establish communication with the host control system.
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