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.
Description
The 6FM1721-3AA20 is a single-axis Positioning Module (WF 721) from the SIMATIC S5-135/155 family. Engineered by Siemens, this module provides high-precision motion control by processing feedback from position encoders. It is highly versatile, supporting both serial and incremental encoder interfaces, which allows it to adapt to various legacy automation setups. Despite being in a phase-out product lifecycle stage, it remains a critical component for the maintenance and operational continuity of older SIMATIC S5 control architectures in heavy industrial sectors.
Features
Technical Specifications
| Attribute | Specification |
|---|---|
| Manufacturer | Siemens |
| Range | SIMATIC S5 |
| Subrange | S5-135/155 |
| Model | 6FM1721-3AA20 |
| Product Type | Positioning Module (WF 721) |
| Controlled Axes | 1 |
| Weight | 0.40kg |
| Dimensions | 25.40 x 2.50 x 20.30 cm |
| Commodity Code | 85389091 |
| PLM Product Phase | Phase-Out |
Installation Guidelines
Global Express Shipping
Returns & Warranty

Description
The 6FM1721-3AA20 is a single-axis Positioning Module (WF 721) from the SIMATIC S5-135/155 family. Engineered by Siemens, this module provides high-precision motion control by processing feedback from position encoders. It is highly versatile, supporting both serial and incremental encoder interfaces, which allows it to adapt to various legacy automation setups. Despite being in a phase-out product lifecycle stage, it remains a critical component for the maintenance and operational continuity of older SIMATIC S5 control architectures in heavy industrial sectors.
Features
Technical Specifications
| Attribute | Specification |
|---|---|
| Manufacturer | Siemens |
| Range | SIMATIC S5 |
| Subrange | S5-135/155 |
| Model | 6FM1721-3AA20 |
| Product Type | Positioning Module (WF 721) |
| Controlled Axes | 1 |
| Weight | 0.40kg |
| Dimensions | 25.40 x 2.50 x 20.30 cm |
| Commodity Code | 85389091 |
| PLM Product Phase | Phase-Out |
Installation Guidelines
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 .
| Color pattern |
Dots
|
| Country of origin |
Germany
|
| Power source |
DC Power
|