Product Details:

MODICON AS-S908-120 is a dedicated remote I/O master processor designed for dual redundant coaxial cable S908 bus, compatible with Modicon 984 legacy PLC platform. It acts as the network master to poll all distributed remote I/O drops on the S908 coaxial network, collecting discrete and analog input signals from field racks and distributing output commands transmitted by the host CPU. The dual-cable design provides communication redundancy, which greatly improves the reliability of critical process control and avoids system shutdown caused by single cable failure. This module communicates with the main controller through the local backplane bus, synchronizing real-time process data continuously. It adopts standard rack mounting for Modicon dedicated backplane, with front panel LED indicators for power, network activity, communication fault and drop status to support fast on-site troubleshooting. Built-in EMC filtering and surge suppression circuits protect the coaxial bus interface from voltage spikes and electromagnetic interference in heavy industrial environments. As an obsolete original spare part, it is used for maintenance and retrofit of legacy Modicon distributed control systems. Direct drop-in replacement keeps the existing dual coaxial cabling, remote drop configuration and backplane layout unchanged, and eliminates the need to rework the whole remote I/O network to cut production downtime.

Basic Parameters

Product type: dual cable S908 remote I/O master processor

Compatible system: Modicon 984 series

Bus type: redundant dual coaxial S908 RIO bus

Max drops: up to 31 remote I/O drops

Scan performance: 3 ms base scan plus extra time per KB of data

Installation: rack mount for Modicon dedicated backplane

Operating temperature: 0°C ~ +60°C

Protection grade: IP20

Supported Functions

Dual redundant S908 bus polling and data forwarding

Automatic switchover between primary and standby cable

Remote I/O drop status monitoring and fault reporting

Backplane high-speed data exchange with host CPU

Real-time I/O data synchronisation

Bus signal conditioning and transient protection

Core Functions

Continuous cyclic polling of all remote I/O nodes

Onboard multi LED for network, run and fault indication

Coaxial bus surge and noise suppression

Redundant cable automatic switching

Data frame verification and retransmission for error recovery

Diagnostic flag storage for bus and drop failures

Hardware Specifications & Environmental Features

Built-in bus noise filtering and surge suppression circuit

Storage temperature: -25°C ~ +70°C

Relative humidity: 5% to 95% non-condensing

Status: Obsolete original part, available for spare replacement

Industry Applications:Applied in legacy petrochemical distributed control, old paper making production automation, water treatment remote signal collection and large conveyor remote I/O control racks.

Note:Confirm dual cable S908 configuration, backplane compatibility and remote drop assignment before ordering.

This is from our current stock.

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