Aastra ROF1376303/1 – DC/DC MX-One Board

Overview

The Aastra ROF1376303/1 is a DC/DC power board used in Aastra (now Mitel) MX-ONE Classic telephony subracks, responsible for distributing and converting the system’s main −48 VDC supply into the regulated voltages that device boards require to operate. It is a core power-distribution component rather than a communication or line card, sitting between the AC/DC power system and the equipment backplane. The MX-ONE platform originated in Ericsson’s enterprise communications business, which is why its boards carry Ericsson-style ROF product numbers; the business passed to Aastra and later to Mitel.

As a maintenance and spares item for existing MX-ONE Classic installations, the Aastra ROF1376303/1 remains a relevant replacement part for facilities keeping legacy Aastra/Mitel telephony infrastructure in service. Seven Star LLC supplies the Aastra ROF1376303/1 as a parts partner to telecommunications, IT and facilities teams across Muscat, Sohar, Salalah and the wider GCC, helping them keep critical voice systems running while longer-term migration plans are prepared.

Operating Principle

The Aastra ROF1376303/1 receives the system’s −48 VDC main supply and distributes it to the MX-ONE Classic backplane, while also generating the regulated ±5 V and ±12 V DC rails that device boards in the subrack require for their internal logic and interface circuits. By centralizing this voltage conversion on a dedicated board, the MX-ONE Classic architecture keeps individual device boards simpler, relying on the DC/DC board for clean, regulated power.

The −48 VDC supply is the traditional telecom standard because it can be backed directly by battery banks, allowing the exchange to continue operating through mains failures. The DC/DC board is therefore the link between this robust battery-backed feed and the sensitive electronics on each device board. If the DC/DC board fails, the boards it supplies lose power, which is why a healthy power board is fundamental to the availability of the whole subrack.

Engineering Design of the Aastra ROF1376303/1

The board is designed to slot directly into an MX-ONE Classic subrack, converting the incoming −48 VDC feed into the multiple regulated voltage rails the backplane’s device boards depend on. When a third-party AC/DC power system is used upstream instead of Aastra’s own, the installation documentation specifies a maximum 15-ampere fuse rating to protect the DC/DC board and downstream circuitry from overcurrent conditions.

Replacement follows normal telecom board-handling practice: the technician confirms the product number and revision on the existing board, follows the site’s procedure for isolating the subrack, uses ESD protection while handling the board, and checks the system status after the replacement board is seated. Because MX-ONE Classic installations are often decades old, confirming the exact product number — here ROF1376303/1 — against the installed unit before ordering avoids compatibility surprises.

Key Features

The Aastra ROF1376303/1 provides the following functions within the MX-ONE Classic system:

• It distributes the −48 VDC main supply to the MX-ONE Classic backplane.
• It generates the regulated ±5 V and ±12 V DC rails needed by device boards.
• It fits directly into the MX-ONE Classic subrack architecture.
• It supports third-party AC/DC power systems when protected by a fuse of no more than 15 A.
• Centralized power conversion keeps individual device board designs simpler.
• It is a genuine Aastra/Mitel replacement part for legacy MX-ONE Classic systems still in active service.
• It works with battery-backed −48 VDC telecom power for continued operation during mains outages.
• Keeping one as a spare protects the availability of an entire subrack of device boards.

Industrial Applications

The Aastra ROF1376303/1 is used to maintain existing Aastra/Mitel MX-ONE Classic telephony installations across offices, control rooms, hospitals, hotels, universities and government facilities in Muscat, Sohar and Salalah that have not migrated to a newer communications platform. As a power-distribution board, its failure can take an entire subrack of device boards offline, making it a critical spare to keep on hand for these systems.

Across the GCC, facilities and IT teams supporting legacy enterprise telephony infrastructure rely on genuine replacement boards like the Aastra ROF1376303/1 to avoid extended downtime on communication systems that remain in active service, particularly where full platform replacement isn’t immediately planned or budgeted. Industrial sites such as refineries, ports and utilities in the Sohar and Salalah economic zones often keep voice systems in service for many years, so a reliable source of spares is an important part of their lifecycle planning.

Because MX-ONE Classic exchanges typically contain several subracks, sites often keep a small stock of the most critical spares — power boards first among them — so that a failed Aastra ROF1376303/1 can be exchanged within minutes rather than waiting for international shipping. Recording the product number, revision and location of every installed power board in the site maintenance log also makes future ordering faster and more accurate, and helps maintenance contractors plan preventive replacements during scheduled maintenance windows.

Technical Specifications

The main specifications of the Aastra ROF1376303/1 are listed below:

Power Capacity and Consumption

Mitel documentation lists the DC/DC board ROF 137 6303/1 as the power unit for the MX-ONE Classic 7U chassis, with a 40 mm front. It distributes the -48 V DC supply from the AC/DC power system to the backplane and generates the ±5 V and ±12 V voltages that the device boards need. The board also has an input for external alarms, which can be wired directly to it in the 7U chassis.

The maximum power available from an MX-ONE Classic chassis depends on the revision of the DC/DC board. Mitel lists 350 W for revisions up to R4A and 720 W for R4B and later. The board itself has a typical power consumption of 12 W and a maximum of 25 W. If a third-party AC/DC power system is used, Mitel states that a fuse of maximum 15 A is required.

Cabling and Installation

In the MX-ONE Classic 7U chassis, the -48 V supply is connected to the DC/DC board with either a single cable (51305286 at 5 m or 51305287 at 12 m) or a splitter cable (50006938 at 5 m or 50006937 at 12 m) that continues on to the fan unit. Mitel instructs that these cables must not be cut and that the shortest cable length between the AC/DC unit and the DC/DC board is 5 meters.

Installation involving power cables, batteries and earthing must follow local regulations, and Mitel requires installation personnel to read the safety instructions beforehand. Because the available chassis power differs between board revisions R4A and R4B, confirm the revision of the installed board before planning capacity. The DC/DC board front also differs in layout from standard device board fronts.

Request a Quote for Aastra ROF1376303/1

To order the Aastra ROF1376303/1 DC/DC MX-ONE board, send Seven Star LLC a formal RFQ with the quantity and the product number and revision shown on your existing board. Our team will confirm availability and lead time, and can quote other legacy MX-ONE spares at the same time for delivery anywhere in Oman and the GCC. Contact our instrumentation and communications division for pricing and technical support.

Browse the full Aastra Technologies range or see more Industrial Communications products supplied by Seven Star LLC in Oman and the GCC.