Description
Allied Telesis AT-MX40F/ST-05 | 10Mbps ST Fiber-Optic AUI Transceiver
Product Introduction
When legacy industrial workstations or PLC racks need to interface with a modern fiber-optic backbone without replacing internal network cards, a direct-attach media converter is mandatory. The Allied Telesis AT-MX40F/ST-05 is not just a standard patch adapter; it is a full-featured micro transceiver that mounts directly onto a 15-pin AUI port, translating electrical frames into light pulses across an ST-connector interface—though physical cabinet clearances must be verified before plug-in.
This unit eliminates the vulnerability of copper cable runs against electromagnetic interference (EMI) on the factory floor. Featuring an automatic receive light level adjustment, it scales across varying fiber lengths up to 2 kilometers without requiring external optical attenuators. Built-in diagnostic LEDs give an instant read on link integrity, collision activity, and internal logic state, making it a reliable bridge for vintage systems.
Key Technical Specifications
| Parameter | Value |
| Standard Compliance | IEEE 802.3 10BASE-FL, FOIRL, Version 1.0/2.0 |
| Media Connector | ST Optical Female (Dual ports: Receive / Transmit) |
| DTE Interface | 15-Pin D-sub Male (AUI plug-compatible) |
| Maximum Distance | Up to 2,000 meters (6,556 ft) on 10BASE-FL |
| Diagnostic Indicators | 6 LEDs: Power, Transmit (TX), Receive (RX), Link (LNK), Collision (COL), Jabber (JBR) |
| Power Supply | Supplied via AUI port (12V DC, 300mA max profile) |
| Dimensions | 6.9cm x 4.2cm x 1.93cm (2.70″ x 1.66″ x 0.76″) |
| Operating Temperature | 0°C to 40°C (Standard industrial cabinet limits) |
Application Scenarios & Pain Points
- Isolating High-Noise Electrical Zones: Running unshielded copper AUI drops past heavy variable frequency drives (VFDs) introduces packet-killing electrical noise. Swapping to the AT-MX40F/ST-05 moves the data stream entirely onto immune glass fiber.
- Connecting Legacy Scada Terminals: Older automation engineering stations often only feature an AUI port. This transceiver plugs straight into the back of the terminal, instantly modernizing its physical media layer to interface with a plant-wide fiber backbone.
- Long-Distance Control Room Links: Copper AUI drop cables are strictly limited to 50 meters. Using this transceiver allows the connection to stretch up to 2,000 meters straight to a remote networking hub without active repeater midpoints.
QA & Live Testing SOP (Trust Signal)
Verifying surplus hardware requires rigorous bench simulation. We test every AT-MX40F/ST-05 by latching it onto a live 10Mbps AUI host port simulator. We inject traffic streams while monitoring the optical output power using an optical loss test set, ensuring the internal transmitter hits standard launch amplitudes (-12dBm to -19dBm range depending on core size). Finally, we verify that the onboard collision and jabber logic circuits trip correctly under fault simulation.
Field Engineer’s Pitfall Guide
- ❗ AUI Cable Length Violations: If you use an external AUI drop cable instead of mounting the transceiver directly to the DTE, ensure it never exceeds 50 meters (164 ft), or signal propagation delays will trigger excessive frame collisions.
- ❗ SQE/Heartbeat Switch Mismatch: Check the internal Signal Quality Error (SQE) switch setting. Leaving the heartbeat enabled when connecting to a multi-port fiber repeater will cause constant link-test failures.
- ❗ Reversed Fiber Polarity: Always cross your fiber strands—ensure the Transmit (TX) port on the transceiver maps directly to the Receive (RX) port on the opposing network device, or the link light will stay dark.
Intent-Driven FAQ
- Can I plug the AT-MX40F/ST-05 directly into an Ethernet switch?
Only if your switch features a legacy 15-pin AUI port. Modern switches use RJ45 or modular SFP slots, meaning you would need an external media converter rather than a direct AUI micro-transceiver.
- Does this transceiver require an external power supply brick?
No. Operating power is drawn directly through the 15-pin AUI D-sub connector from the host device’s internal power pins.
- Will this unit work with single-mode fiber optic cabling?
No. The “/ST” suffix denotes a multimode 10BASE-FL design optimized for 850nm wavelength over multimode fiber. For single-mode applications, look for the corresponding SM variants.
- What does the JBR (Jabber) LED indicate if it lights up?
It indicates that the internal logic has detected a continuous transmission fault (a “jabbering” node) and has automatically shut down the port to protect the rest of the network loop.
- Are these units still actively manufactured?
No, Allied Telesis has phased out this specific generation of micro transceivers. Replacement units are sourced from verified new surplus or tested secondary stock.
