Configured for low-power digital signal switching in SLC 500 rack-based architectures, the Allen-Bradley 1746-OG16 (1746-OG16 Current Sinking TTL Output Module) provides direct physical/electrical execution. This 16-point discrete hardware assembly translates logic-level backplane commands into isolated Transistor-Transistor Logic (TTL) sinking outputs to drive solid-state relays, specialized integrated circuits, and external microprocessor peripherals without signal conditioning interfaces.

Model Catalog Analysis

• Base Part Number 1746-OG16: Designates a 16-channel, 5 VDC nominal TTL sinking output module for the SLC 500 platform.
• Series Revision 1746-OG16/A: Initial hardware release utilizing discrete TTL component layouts and legacy backplane interfaces.
• Series Revision 1746-OG16/B: Updated circuit trace layouts with enhanced immunity to field circuit switching noise.
• Series Revision 1746-OG16/C: Revised ASIC integration for optimized backplane power efficiency and physical component protection.

Physical & Electrical Data

Deterministic Backplane & Bus Communication Integration

The module negotiates signal transfer over the internal SLC 500 chassis backplane bus communication velocity framework, operating deterministically to synchronize output state transitions with processor scan execution. Logic state updates execute across the local rack bus without external signal propagation delay, keeping overall firmware flash compatibility stable across standard 1747 CPU platforms. Low logic level output sinking prevents bus voltage dips, maintaining clean dynamic execution across adjacent high-density I/O modules installed on the same backplane section.

Ordering & Package Contents

• 1 x Allen-Bradley 1746-OG16 Output Module
• 1 x Removable Terminal Block Assembly
• 1 x Installation Instruction Leaflet

Mechanical Installation & Wiring Rules

• Turn off chassis backplane power before inserting or removing the module from the slot.
• Keep 5 VDC TTL signal wiring away from high-voltage AC mains and inductive motor leads.
• Connect external 5 VDC power supply common directly to the designated field ground pin to avoid ground loop noise.
• Limit total conductor run length to less than 3 meters (10 feet) to prevent TTL signal attenuation and ringing.
• Ensure all terminal screws are tightened to a torque of 0.6 N-m (5 lb-in).

Technical Questions & Answers

• What is the primary electrical operating mechanism of the output channels?

  The module operates as a current-sinking device, drawing up to 24 mA per channel toward ground when logic state turns low.

• Can this module switch standard 24 VDC industrial control circuits?

  No. Applying voltages outside the 4.5 to 5.5 VDC range will damage the internal TTL output transistors.

• Does the module allow hot-swapping under powered rack conditions?

  No. Insertion or removal while the backplane is energized can cause unexpected signal glitches or permanent module damage.

• What is the total current draw from the internal 5 VDC backplane bus?

  The module draws a steady-state current of 180 mA directly from the SLC 500 backplane 5 VDC rail.

• What happens if external field supply polarity is wired in reverse?

  Reverse voltage application causes excessive forward diode conduction, blowing internal protective fuses or damaging output circuits.

• How are the 16 output channels structured across field wiring terminals?

  All 16 channels share a common internal ground return logic path routed through the module terminal block.

• How does cable length affect 5 VDC TTL signal transmission integrity?

  Long wire runs introduce line capacitance, causing edge degradation and increased susceptibility to electromagnetic noise.

• Is external circuit protection required for inductive TTL loads?

  Yes. Flyback diodes must be placed across external inductive loads to suppress voltage transients during turn-off events.