# IO modules

> The Voltmasters IO modules give the EMS extra inputs and outputs: the Volt DIO for digital signals and relays, the Volt AIO for analog 4-20 mA signals.

Source: https://voltmasters.io/en/docs/device-integrations/io-modules/

With an IO module the EMS reads signals and switches circuits that do not communicate themselves: a contact, a relay or a 4-20 mA current loop. The controller talks to the module over the network. Voltmasters has two IO modules:

| Module | Signals | What it does |
| --- | --- | --- |
| **[Volt DIO](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/)** | 6 digital inputs and 6 relay outputs | Switches relays and reads the position of contacts. |
| **[Volt AIO](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-aio/)** | 6 analog inputs and 2 analog outputs (4-20 mA), 2 digital inputs and 2 digital outputs | Reads and drives analog current signals. |

![Overview of the IO modules. The controller is connected over the network with Modbus TCP to the Volt DIO and the Volt AIO. The Volt DIO switches a controllable load and an emergency stop circuit, and reads contacts and signals. The Volt AIO receives the setpoints of the Fluvius telecontrol cabinet and sends an echo back.](https://voltmasters.io/assets/docs/io-modules-overview-en.svg)

*The controller talks to both modules over the network. The modules sit in the cabinet, next to what they drive.*

## Applications

| Application | Module |
| --- | --- |
| Switching a [controllable load](https://voltmasters.io/en/docs/device-integrations/controllable-loads/) on and off, such as a heating element or a pump | Volt DIO |
| Executing a [hardware emergency stop](https://voltmasters.io/en/docs/dso-rtu/emergency-stop/) when the grid operator asks for it | Volt DIO |
| Grid operator watchdogs and signals, as with [ORES](https://voltmasters.io/en/docs/dso-rtu/grid-operators/ores/) | Volt DIO |
| The switches, the protection relay and the generator start of a [microgrid](https://voltmasters.io/en/docs/microgrid/) | Volt DIO |
| Analog telecontrol of a [Fluvius telecontrol cabinet version 4](https://voltmasters.io/en/docs/dso-rtu/grid-operators/fluvius/tck4/) | Volt AIO |

## Next steps

[Volt DIO](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-dio/): Add the digital IO module and configure its ports.

 

[Volt AIO](https://voltmasters.io/en/docs/device-integrations/io-modules/volt-aio/): The analog IO module for 4-20 mA signals.

 

[Controllable loads](https://voltmasters.io/en/docs/device-integrations/controllable-loads/): Switch an on/off load through a relay output.