What It Is and Where It Fits
The Siemens 6GT2891-4FH20 is a pre-assembled SIMATIC RF MV plug-in cable that connects an ASM 456, RF160C, RF170C, or RF18XC communication module to an RFID reader, or serves as an extension cable between those modules and readers in the SIMATIC RF, MV, or MOBY PUR families. It's a 2-meter, 6-core trailing cable with M12 8-pin male-to-female straight connectors — the kind of assembly you spec when the reader sits a panel's width away from the communication interface and you need a shielded, factory-terminated link that won't degrade signal integrity.
Key Ratings and What They Mean for Fit
Rated for 300 V maximum, which covers the typical 24 VDC supply used by RFID readers and communication modules with generous headroom — the cable's insulation isn't the limiting factor in a 24 V circuit. The braided shield of tin-plated copper wires keeps common-mode noise from coupling into the reader's data lines; in a noisy cabinet next to drives or contactors, that shield is what preserves the read rate. The cable is flame-resistant per IEC 60332-1-2, so it meets the vertical-wire flame test required for control panels in most industrial installations. It's also grease-resistant and mineral-oil-resistant, which matters when the cable passes through a machine base or runs near hydraulic lines. With 3 million bending cycles and a minimum continuous-bend radius of 75 mm, this cable is designed for trailing applications — think reader heads on a moving gantry or a cable track that follows a linear actuator. The 200 N maximum tensile load means it can handle the pull of a moderate cable carrier without the conductors taking a set.
Sourcing and Lifecycle Reality
The cable carries UL/ETL listing at 300 V with CM (Communications) rating on the cable itself, plus EAC approval for Eurasian Customs Union markets. That CM rating means the cable, when installed without the molded plugs, meets the vertical-tray flame test for plenum and riser applications — useful if the run passes through a cable tray between zones.
Integration Notes
The M12 8-pin straight male-to-female connectors are keyed for the Siemens RF interface pinout — no field wiring, no risk of a swapped pair. The cable sheath is black PVC, halogen-free is not specified (it's not), so if the panel spec demands zero-halogen for smoke density in a manned area, this isn't that cable. Silicon-free, yes, which avoids outgassing issues near paint or bonding lines. Loop resistance is 160 mΩ/m maximum per conductor, so for a 2-meter cable the total loop is under 0.32 Ω — negligible voltage drop for a 24 V reader supply drawing maybe 200 mA. The insulation resistance coefficient of 20 GΩ·m tells you the dielectric is sound for the cable's service life; you won't see leakage current drift as the cable ages in a dry indoor environment.