---
title: "DIN-rail Modbus gateways, meters and relays | GridBit"
description: "Eight DIN-rail Modbus modules: GWU gateways, the MCU-4 three-phase analyser, the RTU-4 astronomical relay, the SMU-3 voltage detector and WDT watchdog relays."
url: "https://www.gridbit.tech/hardware"
language: "en"
translation: "https://www.gridbit.tech/bg/hardware"
---

Hardware

# DIN-rail Modbus modules

Gateways, a three-phase meter, relays and detectors, developed and field tested by GridBit. Every module has a datasheet and a Modbus register map.

- **modules in the range**: 8
- **product families**: 5
- **DIN rail mounting, IEC 60715**: 35 mm

- [GWU-5](https://www.gridbit.tech/hardware/gwu-5)
- [GWU-4](https://www.gridbit.tech/hardware/gwu-4)
- [GWU-2](https://www.gridbit.tech/hardware/gwu-2)
- [MCU-4](https://www.gridbit.tech/hardware/mcu-4)
- [RTU-4](https://www.gridbit.tech/hardware/rtu-4)
- [SMU-3](https://www.gridbit.tech/hardware/smu-3)
- [WDT-1](https://www.gridbit.tech/hardware/wdt-1)
- [WDT-4](https://www.gridbit.tech/hardware/wdt-4)

The range

## Pick a module

- [Gateway GWU-5 4G LTE gateway for Modbus devices, with Ethernet and MQTT 4G LTE Cat 1 Mobile network, 2G fallback RS485 + Ethernet Modbus RTU and Modbus TCP](https://www.gridbit.tech/hardware/gwu-5)
- [Gateway GWU-4 2G/4G gateway for Modbus RTU devices, two digital inputs 4G LTE Cat 1 Mobile network, 2G fallback RS485 Modbus RTU](https://www.gridbit.tech/hardware/gwu-4)
- [Gateway GWU-2 2G GSM/GPRS gateway for Modbus RTU devices 2G GSM/GPRS Mobile network RS485 Modbus RTU](https://www.gridbit.tech/hardware/gwu-2)
- [Meter MCU-4 Three-phase network analyser with Modbus RTU 3P+N / 1P+N Pole configuration U, I, P, cos φ, E Measured parameters](https://www.gridbit.tech/hardware/mcu-4)
- [Relay RTU-4 Astronomical relay with Modbus RTU and energy saving mode Sunrise and sunset Relay schedule 250 VAC Max. relay voltage](https://www.gridbit.tech/hardware/rtu-4)
- [Inputs SMU-3 Eight-channel AC voltage detector with Modbus RTU 8 Voltage detection inputs 280 VAC Maximum input voltage](https://www.gridbit.tech/hardware/smu-3)
- [Watchdog WDT-1 Watchdog relay that restarts devices when Modbus communication stops Normally open Relay contact 250 VAC Max. relay voltage](https://www.gridbit.tech/hardware/wdt-1)
- [Watchdog WDT-4 Modbus watchdog relay, fallback to photo sensor or clock Normally open Relay contact 250 VAC Max. relay voltage](https://www.gridbit.tech/hardware/wdt-4)

Questions

## Short answers

Another question? [Ask an engineer](https://www.gridbit.tech/contact)

### Which modules are in the GridBit hardware range?

The range has eight DIN-rail modules. Three are gateways: GWU-5, GWU-4 and GWU-2. The others are the MCU-4 three-phase network analyser, the RTU-4 astronomical relay, the SMU-3 eight-channel AC voltage detector and the WDT-1 and WDT-4 watchdog relays.

### Which protocol do the modules use?

The modules talk Modbus RTU over RS485. The GWU-5 gateway also reads Modbus TCP devices on its LAN port and sends data with MQTT. One gateway reads up to 127 devices on the bus.

### Which gateway should I choose?

Choose by the network on site. GWU-5 works over 4G LTE Cat 1 with 2G fallback or over Ethernet, and GridBit Cloud manages it remotely. GWU-4 is a 2G/4G gateway with two digital inputs. GWU-2 is a 2G GSM/GPRS gateway for Modbus RTU devices.

### Do the modules work with Modbus devices from other vendors?

Yes. The gateways read any device that talks Modbus RTU on the same RS485 bus, such as meters, controllers and sensors from other vendors. In the EIM system, third-party sensors for humidity, smoke, water and intrusion share the line with the GridBit modules.

### Where do I find the specifications and the Modbus register map?

On the page of each module. It lists the specifications, the meaning of the LEDs, the Modbus registers with a filter, and the dimension and wiring drawings.

## Need a configuration for your site?

Tell us what you measure and control. We answer with the modules, a price and lead time.

[Request a quote](https://www.gridbit.tech/contact) [office@add-bg.com](mailto:office@add-bg.com)