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Small beige box with terminal block and fiber port, single-mode 20km RS232 RS485 RS422 converter

UOTEK

UOTEK UT-277SM RS232 RS485 RS422 Fiber Modem 460kbps 20km

SKU CH-E3PN-19TWD

Converts RS-232, RS-485 and RS-422 signals to single-mode fibre for 20 km links at up to 460 kbps

  • Interface typeOptional SC, FC, ST
  • Cable interfaceTerminal block
  • Maximum transmission rateTransmission rate: 460 kbit/s
  • Product typeFiber Optic MODEM
  • Connects serial devices over 20 km single-mode fiber
  • Converts RS-232, RS-485 and RS-422 to optical signals
  • Supports 460 kbps on RS-485/422 and 115.2 kbps on RS-232
  • Mixed-port flexibility links different serial standards directly
  • Master-slave mode enables reliable half-duplex RS-485 control

Industrial serial-to-fibre bridge

The UT-277SM converts asynchronous RS-232, RS-485 and RS-422 signals for transmission over single-mode fibre up to 20 km. It is built for engineers linking remote terminal units or SCADA controllers across sites where copper runs are impractical. The pair of modems enables full-duplex or half-duplex operation with mixed electrical interfaces on each end.

Low-draw passive cooling

The unit runs without fans and draws minimal power from the supplied US or EU mains adapter, so it adds no audible noise to cabinets or DIN-rail enclosures. Typical surface temperature stays close to ambient during continuous 460 kbps RS-485/422 traffic. No external heatsink or forced airflow is required for normal indoor deployments.

Two modems create the link

A single UT-277SM cannot operate alone; the kit includes two matched units so the optical path is ready immediately. Terminal-block wiring lets you mix RS-232 at 115.2 kbps with RS-485 or RS-422 at 460 kbps on either side without extra converters. Master-slave mode and automatic TXD control on the RS-485 port simplify integration with legacy polling software.

How it compares

Measured against everything we stock in Cable Modems & Gateway Routers, at today’s prices. Recalculated every night.

Price $85.99
Cheaper than about 63% of the 122 comparable items (median $120.99).

Specifications

Product
Brand nameUOTE
Model nameUT-277SM
Product typeFiber Optic MODEM
Ports & slots
Interface typeOptional SC, FC, ST
Cable interfaceTerminal block
More details
Maximum transmission rateTransmission rate: 460 kbit/s

Questions about this item

How do I connect the terminal block for RS-485 and which wiring step is often missed?

Wire the terminal block for two-wire half-duplex RS-485 or four-wire full-duplex RS-422, then enable the TXD control jumper so the modem drives the line only during transmission — skipping this jumper causes bus contention.

Which consumable part will need replacement first in a 20 km single-mode link?

The SC, ST or FC single-mode fiber patch cord and its connector ferrules are the only field-replaceable items; the modem itself has no user-serviceable parts.

At what sustained data rate does the RS-232 port become the bottleneck?

The RS-232 port tops out at 115.2 Kbps, so any continuous stream above that rate will be limited by the port rather than the 460 Kbps fiber link.

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