MLU-1 documentation › Hardware specifications

Hardware specifications

Applies to MLU-1 (rev C and later) and MLU-1P · reviewed 2026-07-02

Two models, one software

Both models run the same software and are configured identically. The difference is power and storage, and it only matters in two situations: a comms cabinet with no free socket, and a site with secure release printing for more than about sixty people.

Model	Power	Storage	Use it when
MLU-1	12 V DC external supply	32 GB eMMC	Default. Meter collection, alerts, release printing for a normal floor.
MLU-1P	PoE (802.3af) or 12 V DC	128 GB eMMC	Cabinet installs with no mains socket, or heavy release printing where held jobs need room.

Specification table

Processor	Quad-core ARM Cortex-A55, 1.6 GHz, fanless
Memory	2 GB LPDDR4
Storage	32 GB eMMC (MLU-1) / 128 GB eMMC (MLU-1P), industrial grade, wear levelling
Network	2 × 1000BASE-T. eth0 = site LAN, eth1 = service port, fixed at 192.168.77.1/24
Other ports	1 × USB-A 2.0 (backup and recovery media), 1 × micro-USB serial console (115200 8N1)
Indicators	Three LEDs: power, status, activity. Patterns are listed in diagnostics.
Power draw	5 W typical, 9 W peak during an upgrade
Dimensions	108 × 82 × 26 mm, 240 g
Mounting	DIN rail clip (supplied), wall bracket (supplied), or flat on a shelf. Not rack ears — the unit is too small to span a rack and hangs badly from a shelf edge.
Operating temperature	0 to 45 °C ambient, 10–90 % RH non-condensing
Clock	Real-time clock with a soldered cell, holds time for about 30 days unpowered
Software	PrintDoc MLU firmware line 3.x. Current release documented here: 3.4.2

Ports and connectors

Looking at the unit with the LEDs towards you, left to right: power inlet, eth0, eth1, USB-A, micro-USB. The two Ethernet sockets are identical and unlabelled on rev C units, which is the single most common installation mistake — see cabling.

Mark the cables. Put a label on the site LAN cable at the unit end during the install. When somebody swaps the two later, discovery finds nothing, the console is unreachable from the LAN, and the first assumption is always that the unit has died.

Sizing: how many devices per unit

The limit is not the processor, it is how long a full polling pass takes. The numbers below are measured on a flat network with SNMP allowed end to end.

Devices	Full meter pass	Recommendation
up to 60	under 1 min	Comfortable on either model.
60–150	2–4 min	Standard site. Leave the default 4-hour schedule.
150–250	6–11 min	Supported. Stagger scan ranges as described in discovery.
above 250	—	Second unit. Two units on one site do not talk to each other and do not need to; split by subnet, never by floor.

Secure release printing is sized separately, by held data rather than by device count. Budget 60 MB per active user per day and check retention before promising a long hold window on an MLU-1.

Where it may and may not live

Comms cabinet, DIN rail: ideal. Watch the ambient temperature at the top of a closed cabinet in summer — we have measured 49 °C in a cupboard that felt fine at knee height.
Wall bracket behind the MFP: fine, and it keeps the unit near the devices it polls. Leave the LEDs visible; a diagnostic call that starts with “what colour is the status light” is much shorter than one that does not.
On top of a printer: no. Laser fusers push hot air straight up, and the unit will spend its life at the edge of its temperature range.
Under a desk on the floor: no. It gets kicked, and the power barrel jack is the part that gives up first.