Mitsubishi A1SY42 Digital Output Local Unit Module

Overview

The A1SY42 is a digital output local unit module in the MELSEC-A series. Mitsubishi’s product-shop listing identifies it as a 64-point digital output local unit with 24 VDC sink outputs, and Mitsubishi A-series I/O manuals describe it more specifically as a Transistor Output Module (Sink Type) with 64 output points.

The same Mitsubishi manual family also shows key electrical details including 12/24 VDC rated load voltage, 10.2 to 30 VDC operating load voltage range, 0.1 A per point, 1.6 A per common, and photocoupler isolation.

Technical Data

Application Value

The A1SY42 fits well in legacy MELSEC-A control racks, machine automation cabinets, conveyor systems, utility panels, and installed Mitsubishi PLC systems where many digital outputs must be driven from a single local rack module.

Because it is a 64-point sink transistor output unit, it is especially practical in cabinets already wired around 12/24 VDC sink-output conventions and dense rack I/O allocation.

This is an engineering inference based on the published 64-point transistor sink-output design and MELSEC-A local-unit role.

Its maintenance value is also strong. Mitsubishi’s product-shop listing marks the part as discontinued, which is consistent with the role it now plays in spare-parts sourcing, retrofit support, and preservation of existing A-series installations.

In those cases, exact module continuity is often far more useful than trying to adapt a different output family into the same rack.

Replacement and Selection Perspective

For replacement work, the A1SY42 should be matched by output point count, sink-output type, voltage class, and MELSEC-A rack role, not just by the module’s general size.

In practical terms, the details that matter most are 64 transistor outputs, sink type, 12/24 VDC load class, and the original common-current structure.

Matching the same model is usually the safest way to preserve field wiring and output behavior.

FAQ

Q1: What kind of module is A1SY42?
It is a MELSEC-A digital output local unit module with 64 transistor outputs in sink type configuration.

It is intended to drive field DC loads from a Mitsubishi A-series PLC rack.

Q2: What applications fit it best?
It fits installed Mitsubishi MELSEC-A automation systems where many DC outputs must be controlled from a single local rack slot.

This is an engineering inference based on the module’s published 64-point local-output design.

Q3: Why is the sink transistor output type important?
Because the field wiring and load behavior are built around that exact output style.

If the installed machine expects sink transistor outputs, replacing the module with a different output type can create immediate wiring and commissioning issues.

Q4: Why do per-point and per-common current ratings matter?
Because they define how the module can be loaded in real operation. Even if each point supports a certain load, the common-current limit still affects how outputs can be grouped and wired in the cabinet.

This is an engineering inference based on the published 0.1 A/point and 1.6 A/common limits.

Q5: What should be checked before ordering?
Check the installed part number, confirm the 64-point sink output requirement, verify the 12/24 VDC load class, and make sure the cabinet is built around the same MELSEC-A local rack arrangement.