Q: Is this module compatible with SIMATIC S7-400 PLCs?
A: Yes, it is designed for the S7-400 family; verify rack and connector compatibility.
1 actual photo shown first. Reference images are model-matched and must be confirmed before purchase.
Siemens
6ES7421-1FH00-0AA0
SIMATIC S7-400 SM 421 Digital Input Module, 16 DI, Optically Isolated
Siemens
From $382.72In stockDiscontinued
Product Description
The SIMATIC S7-400 SM 421 digital input module (MPN 6ES7421-1FH00-0AA0) provides 16 optically isolated channels for reliable acquisition of binary signals in industrial control systems. Designed for the S7-400 platform, it supports robust signal integrity and galvanic separation between inputs and the backplane to minimize interference and fault propagation. Typical applications include interfacing sensors, switches, and field contacts in distributed PLC architectures where high availability and deterministic behavior are required. The module integrates with S7-400 racks and uses a 40‑pin front connector for fast installation and service. Depending on source data, versions are documented with either 120/230 V AC inputs or 24 V DC inputs; verify voltage before deployment. Mechanical form factor suits standard S7-400 slots with IP20 protection for cabinet-mounted environments. Package contents generally include the module; front connector and accessories may be ordered separately.
Key Features
- •16-channel digital input module
- •Optical isolation on all input channels
- •Galvanic isolation to backplane bus
- •Designed for SIMATIC S7-400 systems
- •40-pin front connector interface
- •IP20 protection for cabinet installation
Buy Options
Condition, indicative price, stock, and lead time. Confirm current availability via RFQ.
ConditionPriceAvailabilityLead time
New
Price: $478.4
Availability: 1 in stock
Lead time: Ships from stock
Never Used
Price: RFQ
Availability: Sourced on request
Lead time: Quoted after RFQ
Used
Price: $382.72
Availability: 2 in stock
Lead time: ~6 day lead
Specifications
- Manufacturer
- Siemens
- Model Number
- SM 421 Digital Input Module
- Manufacturer Part Number
- 6ES7421-1FH00-0AA0
- Series
- SIMATIC S7-400
- Number of Inputs
- 16 digital inputs
- Input Type
- Optically isolated
- Front Connector
- 40-pin
- Protection Class
- IP20
- Dimensions
- Approx. 25 x 290 x 219 mm
- Operating Temperature
- 0°C to 60°C
- Storage Temperature
- -40°C to 70°C
- Weight
- Approx. 0.45–0.82 kg (source-dependent)
- Tariff Code
- 85389091
- Part #
- 6ES7421-1FH00-0AA0
- Category
- PLCs/Machine Control
- Category
- PLC Module/Rack
- Weight
- 1.26 lbs
Before we quote this part
Actual photos when available
Nameplate, condition, and visible wear can be shared before quote when stock photos are not enough.
Test notes for used units
Power-on or function test status is stated when available, with clear condition grading.
Trackable global shipping
DHL, FedEx, UPS, or forwarder options can be quoted with packing photos and tracking details.
Clear DOA boundary
For tested units, quote terms can include 7-day DOA support unless otherwise stated.
Independent sourcing disclaimer
We are not an authorized distributor, reseller, or representative of Siemens, Mitsubishi, Omron, or other manufacturers listed on this site. All product names, trademarks, brands, and logos are the property of their respective owners. Products may be used, refurbished, surplus, or sourced from the secondary market unless otherwise stated.
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FAQ
Q: How many input channels are provided?
A: 16 optically isolated digital inputs.
Q: What front connector is required?
A: A 40-pin front connector; typically ordered separately.
Q: What is the protection rating?
A: IP20, suitable for installation within control cabinets.
Q: What input voltage does this module support?
A: Sources conflict between 24 V DC and 120/230 V AC; confirm voltage for your variant before use.