Implementing 3-Switch XOR Ladder Logic with Internal Bit
Implement a 3-SPST switch XOR light circuit in LogixPro or RSLogix 500 using an internal relay bit. Includes truth tables, boolean equations, and verified.
Engineered as a robust hardware expansion, the Beckhoff C9900-E781 push-button extension provides direct tactile operator controls for CP6xxx and CP7xxx Series Control Panels and Panel PCs. This module is specifically optimized for integration below 15-inch displays without integrated keyboards, enhancing operator interface efficiency in demanding industrial environments.
The unit features 16 square push-button keys equipped with individual signal lamps, allowing clear status feedback for machine functions. For safety-critical operations, a dedicated emergency stop key is integrated directly into the faceplate. Communication and control of the push-buttons and indicator lights are managed over a high-speed USB interface, while auxiliary terminal rows allow for direct hardwiring of critical signals to ensure system-wide redundancy and safety compliance.
| Manufacturer | Beckhoff Automation |
| Part Number / Model | C9900-E781 |
| Compatible Displays | 15-inch displays without keyboard (CP6xxx and CP7xxx series) |
| Push-Buttons | 16 x Siemens Signum square (30 x 30 mm) with signal lamps |
| Emergency Stop | 1 x Siemens Signum, directly wireable |
| Selector Switch | 1 x Gray code switch, 23 positions (USB controlled) |
| Control Interfaces | USB (for push-buttons, indicator lights, and Gray code switch) |
| Hardwired Interfaces | Terminal row (second NO contact for all push-buttons, direct E-stop wiring) |
| Front Interfaces | 2 x USB 2.0 Type-A with IP65 screw cap |
| Mounting Location | Below the Control Panel / Panel PC |
| Approximate Weight | 5.0 kg |
| Interface Type | Function and Configuration |
|---|---|
| Internal USB Connection | Transmits first NO contact of 16 push-buttons, Gray code switch state, and drives all indicator lamps. |
| Terminal Block Row | Provides direct hardwired access to the second NO contact of each of the 16 push-buttons. |
| Emergency Stop Terminals | Dedicated terminals for hardwiring safety relays or fail-safe PLC inputs. |
| Front USB Ports | Dual-port pass-through USB A connection protected by an IP65 screw cap. |
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Returns & Warranty

Engineered as a robust hardware expansion, the Beckhoff C9900-E781 push-button extension provides direct tactile operator controls for CP6xxx and CP7xxx Series Control Panels and Panel PCs. This module is specifically optimized for integration below 15-inch displays without integrated keyboards, enhancing operator interface efficiency in demanding industrial environments.
The unit features 16 square push-button keys equipped with individual signal lamps, allowing clear status feedback for machine functions. For safety-critical operations, a dedicated emergency stop key is integrated directly into the faceplate. Communication and control of the push-buttons and indicator lights are managed over a high-speed USB interface, while auxiliary terminal rows allow for direct hardwiring of critical signals to ensure system-wide redundancy and safety compliance.
| Manufacturer | Beckhoff Automation |
| Part Number / Model | C9900-E781 |
| Compatible Displays | 15-inch displays without keyboard (CP6xxx and CP7xxx series) |
| Push-Buttons | 16 x Siemens Signum square (30 x 30 mm) with signal lamps |
| Emergency Stop | 1 x Siemens Signum, directly wireable |
| Selector Switch | 1 x Gray code switch, 23 positions (USB controlled) |
| Control Interfaces | USB (for push-buttons, indicator lights, and Gray code switch) |
| Hardwired Interfaces | Terminal row (second NO contact for all push-buttons, direct E-stop wiring) |
| Front Interfaces | 2 x USB 2.0 Type-A with IP65 screw cap |
| Mounting Location | Below the Control Panel / Panel PC |
| Approximate Weight | 5.0 kg |
| Interface Type | Function and Configuration |
|---|---|
| Internal USB Connection | Transmits first NO contact of 16 push-buttons, Gray code switch state, and drives all indicator lamps. |
| Terminal Block Row | Provides direct hardwired access to the second NO contact of each of the 16 push-buttons. |
| Emergency Stop Terminals | Dedicated terminals for hardwiring safety relays or fail-safe PLC inputs. |
| Front USB Ports | Dual-port pass-through USB A connection protected by an IP65 screw cap. |
Global Express Shipping
Returns & Warranty
Orders are processed and delivered Monday-Friday (excluding public holidays).
For full eligibility, restocking fees, and international return details, please view our official Refund & Return Policy .
| Country of origin |
Germany
|