ABB · TU840
ABB TU840 Redundant Optical ModuleBus Modem Termination Unit
ABB TU840 passive MTU for redundant TB840/TB840A Optical ModuleBus
modem configuration with dual electrical ModuleBus, redundant I/O
and 24 V DC input.
TypeRedundant modem termination unit
SystemABB S800 I/O / Optical ModuleBus
FocusRedundant TB840/TB840A and I/O
BrandABB
TU840 availability, lead time and order review
Send RFQProduct Introduction
TU840 is the passive S800 I/O termination unit for a redundant
TB840/TB840A Optical ModuleBus modem configuration with two
electrical ModuleBus connections and redundant I/O.
Engineering note: TU840 provides module redundancy but ABB records cable redundancy
as No. Keep network redundancy and I/O redundancy as separate
engineering checks.
Technical Specifications
Select a category to view its specifications. All categories are
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Identification & configurationView 6 specificationsHide specifications⌄
| ABB article number | 3BSE020846R1 |
|---|
| Product type | Passive Module Termination Unit |
|---|
| Modem positions | Two TB840/TB840A |
|---|
| Electrical ModuleBus | Two |
|---|
| I/O arrangement | Redundant I/O |
|---|
| Cluster address | Rotary switch, 1 to 7 |
|---|
Redundancy & powerView 5 specificationsHide specifications⌄
| Module redundancy | Yes |
|---|
| Cable redundancy | No |
|---|
| Power arrangement | Single power |
|---|
| Power input | 24 V DC (19.2–30 V DC) |
|---|
| Hot swap | No |
|---|
Terminals, insulation & sizeView 7 specificationsHide specifications⌄
| Acceptable wire size | Solid/stranded 0.2–2.5 mm², 24–12 AWG |
|---|
| Recommended terminal torque | 0.5 Nm |
|---|
| Dielectric test voltage | 500 V AC |
|---|
| Rated insulation voltage | 50 V |
|---|
| Dimensions | 124 × 186.5 × 47 mm |
|---|
| Weight | 450 g |
|---|
| Protection rating | IP20 |
|---|
Compatibility & Replacement
Confirmed modem fit. ABB specifies TU840 for redundant configuration of TB840/TB840A
Optical ModuleBus modems.
Redundancy boundary. TU840 is the ABB configuration for redundant modem positions and
redundant I/O with single power. It does not provide cable
redundancy.
Applications & Fault Scenarios
01Redundant Optical ModuleBus stations
Hosts two TB840/TB840A modem positions and dual electrical
ModuleBus paths for redundant I/O service.
02Controller-room to field I/O continuity
Used at an Optical ModuleBus cluster where loss of one modem must
not remove the redundant I/O arrangement.
03Both modem paths unavailable
Check the 24 V input, single-power feed, cluster address and TU840
seating before treating both modems as failed.
04Redundancy alarm with I/O still running
Compare primary/secondary modem status and both electrical
ModuleBus connections; the plant may be operating without its
intended reserve.
05Unexpected cluster after maintenance
Verify the rotary cluster address is restored to the documented
value from 1 to 7.
AMIKON SUPPORTIndependent spare-parts support
Amikon can review the exact part number, installed system,
quantity, destination and required date before quotation.
Pre-outage checkpoints
- Record the cluster address before removal.
- Confirm both modem positions are TB840/TB840A.
- Document both electrical ModuleBus connections.
- Test the approved redundancy procedure after restoration.
Amikon Supply & Service
Independent multi-brand support for maintenance, outage and
legacy-system requirements.
Order reviewPart number, quantity, destination, required date and system model
checked.
Inspection & testingLabel, condition and serial checks; testing when agreed.
Packing & dispatchProtective export packing and delivery coordination.
DOA, returns, warranty & supportAfter-sales review under the quoted return and warranty terms.
Request for Quotation
- Part Number
- Quantity
- Destination
- Required Date
- Machine / System Model
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These models are listed only as independent sourcing references.
They are not substitutes for TU840. Compatibility, configuration
and stock must be confirmed separately for each item.
TU840 FAQ
What should be checked before ordering ABB TU840 for a redundant
station?
Confirm the exact TU840 identity, the installed S800 I/O
arrangement and the redundancy or optical ModuleBus role against
the applicable ABB documents. Share cabinet and label photos for
order review.
Does an ABB TU840 quotation automatically include every accessory
shown in a system drawing?
No. Included hardware is quotation-specific. Ask for a written
packing-list confirmation of the termination unit and any required
companion items before purchase.
Can current stock, condition and lead time for ABB TU840 be
confirmed from this page?
No. Stock, condition, inspection scope and lead time change by
offer and must be confirmed in the live quotation for ABB TU840.
What pre-shipment evidence can I request for ABB TU840?
Request clear label, condition and serial-number photos plus the
agreed inspection or testing record for ABB TU840 before dispatch.
How should I submit an urgent shutdown requirement for ABB TU840?
Send the exact part number, quantity, destination, required date,
machine or system model and failure context. Priority routing
starts after the ABB TU840 identity is confirmed.
What DOA, return and warranty terms apply to ABB TU840?
They are defined in the quotation. If ABB TU840 arrives DOA or does
not match the purchase order, report the serial number, label,
packaging and fault evidence promptly for after-sales review.
