With the S7-400 automation systems, which are scalable via different types of CPU, you have an alternative to AS 410 automation systems. The systems that can be used in plants with SIMATIC PCS 7 V7/V8 can be classified as follows:

• Standard automation systems
• High availability automation systems
• Safety-related automation systems

Standard automation systems

The AS 414?3, AS 414?3IE, AS 416?2, AS 416?3, AS 416?3IE and AS 417?4 standard automation systems are extremely robust and feature high processing and communication performance.

The AS 414-3 and AS 414-3IE are tailored for smaller-scale applications with smaller quantity structures. This allows for a low-cost starter solution with a modular and scalable system based on the S7-400 controller range. Larger quantity frameworks can be implemented with the AS 416-2, AS416-3/416-3IE and AS 417-4 automation systems. These systems are preferred for medium and large-sized plants.

High availability automation systems

The aim in using high availability automation systems is to minimize the risk of a production outage. In accordance with their basic design, these systems are categorized as:

• AS Single Stations: AS 412-5-1H, AS 414?5?1H, AS 416?5?1H, and AS 417?5?1H with only one CPU, e.g. for the following applications:
  • Subsequent expansion to a redundant system
  • Redundant configuration on UR1 racks, comprising 2 single stations, 4 sync modules, and 2 sync fiber-optic cables
• AS Redundancy Stations: AS 412?5?2H, AS 414?5?2H, AS 416?5?2H and AS 417?5?2H with two redundant CPUs, mounted on one common rack (UR2?H) or two separate racks (UR2)

Safety-related automation systems

Safety-related automation systems (F/FH systems) are available for safety-relevant applications in which an incident can result in danger to persons, plant damage or environmental pollution. These are based on the hardware of the high availability automation systems, which is expanded by safety functions with S7 F systems.

In accordance with the design variant, they are categorized as:

• AS Single Stations
  AS 412F, AS 414F, AS 416F, and AS 417F with only one CPU (safety-related)
• AS Redundancy Stations
  AS 412FH, AS 414FH, AS 416FH, and AS 417FH with two redundant CPUs (safety-related and high availability)

The safety-related F/FH systems collaborate with safety-related F modules of the ET 200 distributed I/O systems or fail-safe transmitters connected directly via the fieldbus to detect not only faults in the process, but also their own, internal faults. They automatically transfer the plant to a safe state in the event of a fault. The redundancy of the FH systems is only used to increase the availability. It is not relevant to processing of the safety functions and the associated fault detection.

All F/FH systems are TUV-certified and comply with the safety requirements up to SIL 3 according to IEC 61508.