The ABCU-402A is a dual-port full-duplex, Gigabit Ethernet, ADAU Overhead module, packet programmer and an IPv4 data packets transmitter.

The ADAU Overhead module supports chassis programming via Ethernet using Trivial File Transfer Protocol (TFTP). Synchronization with an external PTP Grandmaster is achieved using IEEE 1588-2004 Precision Time Protocol version 1 (PTPv1) or IEEE Std 1588-2008 Precision Time Protocol version 2 (PTPv2). The ABCU-402A can also act as a PTPv1 or PTPv2 Grandmaster. The ABCU-402A also supports synchronization via an AGPS-401A module.

In acquisition mode, some or all acquired data is transferred from the backplane to the CVT. Onboard, it is packetized into a DARv3 or IRIG-106 Ch.10 application layer packet. Assembled packets can be transmitted simultaneously on either or both Ethernet outputs. For asynchronous bus data, the ABCU-402A supports aperiodic transmission for efficient bandwidth use, whereby packets are not generated unless fresh data has been acquired from a packetizer user-module.

The ABCU-402A supports routing Ethernet frames received from either Ethernet port to modules in the chassis. This feature allows Ethernet packets to be sent directly to a recorder or PCM transmitter module (among other modules).