This listing is a complete DS3820MAUD1A1B media access module, supplied new-surplus in factory packaging and built around the DS3800HMAC1G1E media access board. In a GE Speedtronic Mark IV, this is the assembly that connects a panel to the system communication bus and controls its access to that shared network. It is cleaned and tested with a one-year warranty.

The DS3820MAUD media access unit and its HMAC board

GE describes the DS3820MAUD as a Mark IV system bus module. Physically it is an interface panel mounted on the DS3800HMAC printed circuit board: the panel carries the cable ports and status windows, while the board underneath holds the electronics — including a bank of red LEDs, ten jumper switches, and the crystal-timed logic that manages bus access. The module ties a Mark IV panel onto a redundant communication bus using two independent paths, labeled Cable A (ports JB and JC) and Cable B (ports JD and JE), with a link-controller connection at JA and power in at JG. That redundancy is deliberate: the <R>, <S>, <T> and <C> cores in a Mark IV depend on continuous communication, and dual cabling keeps them talking if one path is disturbed.

Read the status LEDs before condemning the module

One of the most useful things about this module is that it tells you a great deal before you ever pull it. The panel has three status windows — Cable A OK, Cable B OK, and Watch Dog Timer OK — driven by the LEDs on the HMAC board. Use them:

• If one cable indicator is out but the other is lit, suspect that cable or its far-end segment before the module itself; the redundant path is doing its job.
• If the Watch Dog Timer indicator is not healthy, the board's own logic may have stopped — but confirm the JG power feed first.
• Check that the JA link-controller connector and the Cable A and Cable B connectors are fully seated.
• Verify the ten jumper switches match the module you are replacing; a mismatch will keep a good board off the bus.

Only after the cabling, power, watchdog status and jumpers are accounted for should the module be treated as failed.

Module versus board: what DS3820MAUD1A1B includes

It is worth being precise about what you are buying. The DS3820MAUD1A1B is the full media access module — the interface panel and the DS3800HMAC board together — whereas a DS3800HMAC ordered on its own is just the underlying circuit board. This unit is the complete module and encloses a DS3800HMAC1G1E board. When you request a quote, tell us whether you need the whole module or only the board, since the two are ordered differently.

Decoding the DS3820MAUD and DS3800HMAC numbers

Both numbers follow GE's scheme. DS3820 designates the module and assembly level and MAUD its media-access function, with 1A1B as the group/revision. On the board inside, DS3800 is the Mark IV board series, HMAC the media-access function code, and 1G1E the board revision. Match the suffixes to what is installed, or ask us to confirm compatibility. Our GE Speedtronic Part Number Decoder explains how each field is constructed.

What to tell us for a 24-hour quote

To move quickly, send:

• The full module number with suffix (DS3820MAUD1A1B) and the HMAC board revision if you need a specific one.
• A photo of the panel label — it identifies the module and its revision.
• The turbine and Mark IV panel the module serves.
• Quantity, and whether the unit is down or this is a spare.

Request a Quote for a response within 24 hours. We ship worldwide DDP, accept purchase orders from qualified accounts, and can also quote the companion DS3800HDRA line driver/receiver board that shares the communication path.

General Information about the Product
Part Number	DS3820MAUD1A1B Mark IV DS3800
Description	DS3820MAUD1A1B by GE DS3820MAUD with DS3800HMAC1G1E Media Access Module NEW
Condition	newSurplusFactoryPackage Cleaned and Tested. With 1 Year Warranty.