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Transparent compact smart relay housing with LCD display, 2.8 by 4.24 by 2.34 inches

Schneider Electric

Schneider Electric SR2B121B Compact Smart Relay 8 In 4 Out

SKU CH-59ET-TWZS2

A compact smart relay with 8 inputs, 4 relay outputs, 16 counters, 16 timers, a clock and an LCD display

  • TypeIndustrial Electrical Controls & Automation
  • ColorTransparent
  • Compact automation with 8 inputs and 4 relay outputs
  • 16 built-in timers and 16 counters for sequencing logic
  • Real-time scheduling via integrated clock function
  • Clear status monitoring on LCD display panel
  • Space-saving 2.8 × 2.34 × 4.24 inch DIN-rail footprint

Schneider Electric SR2B121B Smart Relay

The Schneider Electric SR2B121B is a compact smart relay designed for small-scale automation tasks. It provides eight discrete inputs and four relay outputs in a single DIN-rail module. The unit includes an LCD display for local status viewing and parameter editing. It suits installers who need basic logic, timing and counting without a full PLC.

Suited for simple sequencing and monitoring

This relay fits applications such as lighting control, pump sequencing or gate automation where 16 counters and 16 timers are sufficient. The 24 V AC supply requirement means panels built for other control voltages will need a separate transformer. Buyers who need analog I/O, communication ports or more than four output channels should look at larger programmable controllers.

8 A relay output rating

Each of the four outputs can switch up to 8 A, which determines the maximum load the module can drive directly. Loads exceeding this current require an interposing contactor or solid-state relay. The 2.8 in width, 4.24 in height and 2.34 in depth define the DIN-rail space needed in the enclosure.

Highlights

  • Compact automation with 8 inputs and 4 relay outputs
  • 16 built-in timers and 16 counters for sequencing logic
  • Real-time scheduling via integrated clock function
  • Clear status monitoring on LCD display panel
  • Space-saving 2.8 × 2.34 × 4.24 inch DIN-rail footprint

Specifications

BrandSCHNEIDER ELECTRIC
TypeIndustrial Electrical Controls & Automation
ColorTransparent

Questions about this item

How is the SR2B121B wired into a 24 V AC control panel, and what terminal mistake causes erratic operation?

Mount the relay on a DIN rail, connect the eight inputs and four relay outputs to the screw terminals, and supply 24 V AC to the power terminals; the step most often missed is tightening each terminal to the specified torque so vibration cannot loosen a connection.

Which parts of the SR2B121B will need attention or replacement after extended service?

The four electromechanical output relays are rated for 8 A switching; their contacts wear over time and will eventually require relay-module replacement, while the internal clock battery should be checked during routine maintenance.

What is the first limit reached when the SR2B121B runs continuous logic with all counters and timers active?

The program memory holds 16 counters and 16 timers; once all are used the relay cannot accept additional function blocks, so logic capacity is the first constraint under sustained use.

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