1. Introduction

• Function: Monitors 120 VAC discrete field devices (switches, contactors, relay contacts)

• Architecture: Fully triplicated TMR (3‑2‑0) + per‑channel 1oo2D hardware voting

• Safety Certification: IEC 61508 SIL 3 / SIL 4

• Coating: Acrylic conformal coating (T8424C only)

• Operating Temperature: –40 °C to +70 °C (T8424: 0 °C to +60 °C)

• Channels: 40 × 120 VAC digital inputs

• Isolation: 2500 VDC optical isolation (channel‑to‑channel, channel‑to‑system)

• SOE Resolution: 1 ms

• Hot‑Swap: Supported

2. Product Overview

• 40 channels of isolated 120 VAC digital input

• Triple modular redundancy (TMR) for fault‑tolerant operation

• Per‑channel 1oo2D voting for fault detection and isolation

• Sigma‑delta ADCs for precise voltage measurement

• 2500 VDC optical isolation between field and backplane

• Onboard SOE (Sequence of Events) logging with 1 ms resolution

• Per‑channel open/short circuit detection

• Conformal coating for harsh environments (T8424C)

• Wide operating temperature range: –40 °C to +70 °C

• Front‑panel LED status indicators

• Hot‑swap capable for online replacement

• Compatible with T8100 / T8400 Trusted controller chassis

3. Specifications

3.1 Mechanical

• Form Factor: T8000 chassis module, 56 mm wide, 6U height

• Dimensions (H × W × D): 255 mm × 56 mm × 210 mm

• Weight: 1.3 kg (2.87 lbs)

• Mounting: T8100 / T8400 chassis slots 1–16

• Connectors: Front‑panel terminal blocks TB1–TB5 (8 channels each)

• PCB Protection: Acrylic conformal coating (T8424C)

3.2 Electrical

• System Supply: 20–32 VDC (nominal 24 VDC)

• Power Consumption: ≤ 5 W

• Input Channels: 40 × 120 VAC digital inputs

• Input Voltage Thresholds:

  • Logic 1: 90–150 VAC

  • Logic 0: < 30 VAC

• Input Current: Approximately 4 mA per channel at 120 VAC

• Input Type: Sink (NPN) / Source (PNP) configurable

• Isolation: 2500 VDC optical barrier

• Backplane Interface: Trusted Backplane Bus (TBB), TMR

3.3 Functional

• Voting: 1oo2D per channel (triple measurement + comparison)

• SOE Resolution: 1 ms per channel state change

• Diagnostics:

  • Open‑circuit detection (per channel, with line resistor)

  • Short‑circuit detection (per channel)

  • Onboard BIST (Built‑In Self‑Test)

  • Fault logging to system HMI

• Response Time: ≤ 2.0 ms channel‑to‑backplane

• Data Integrity: BER < 10⁻¹²

3.4 Environmental (T8424C Rated)

• Operating Temperature: –40 °C to +70 °C

• Storage Temperature: –40 °C to +85 °C

• Humidity: 5–95 % RH, non‑condensing

• Altitude: ≤ 2000 m

• Vibration: IEC 60068‑2‑6 (1 g, 10–150 Hz)

• Shock: IEC 60068‑2‑27 (15 g, 11 ms)

3.5 Safety & Certification

• Safety Standard: IEC 61508 SIL 3 / SIL 4

• Certifications: CE, UL, CSA, ATEX II 3G Ex ec IIC T4 Gc, IECEx

• Fault Tolerance: TMR (3‑2‑0), 1oo2D per channel

• PFHd: < 8.0 × 10⁻¹⁰ / hour (SIL 4)

4. Front Panel Indicators

• PWR (Green): ON = module power healthy; OFF = no power

• RUN (Green): ON = module active; FLASHING = initialization / BIST

• FAULT (Red): ON = critical fault; FLASHING = minor fault

• COM (Green): FLASHING = backplane communication active

• TB1–TB5: Terminal blocks for 40 input channels

• FG: Functional ground (chassis earth)

5. Installation

• Chassis: Insert into any vacant slot in T8100 or T8400 Trusted chassis

• Hot‑Swap: Supported; no system shutdown required

• Mounting Torque: 0.8–1.0 Nm for front‑panel screws

• Orientation: Ensure correct alignment with backplane connectors

6. Wiring

• Terminal Blocks: TB1–TB5 (8 channels each)

• Field Wiring:

  • Connect 120 VAC line (L) to group common terminal

  • Connect field device output to channel input terminal

  • Connect device common to 120 VAC neutral (N)

• Wire Gauge: 16–22 AWG stranded

• Terminal Torque: 0.5–0.6 Nm

• Line Resistor: 10 kΩ per channel for open‑circuit monitoring

7. Operation

• Power‑Up: PWR ON; RUN flashes during BIST (5–10 seconds)

• Normal Operation: PWR and RUN steady green; FAULT OFF; COM flashing

• Fault Conditions:

  • FAULT ON: critical fault (short circuit, TMR mismatch)

  • FAULT FLASHING: minor fault (single‑lane mismatch)

• SOE Logging: All state changes time‑stamped at 1 ms resolution

8. Ordering Information

• T8424: Standard 40‑Ch 120 VAC DI (0 °C to +60 °C)

• T8424C: Conformal coated, –40 °C to +70 °C

• TC‑8424: Terminal block cable kit

• T8100 / T8400: Trusted controller chassis