This page walks through the physical hardware of the RELO IO8: what comes in the box, where everything is located, and what each connector does. Reading this before powering up helps avoid common wiring mistakes.
In the box
- 1 × RELO IO8 unit
- 2 × 9-position screw-terminal blocks (relay outputs)
- 1 × 9-position screw-terminal block (digital inputs)
- 1 × IEC C14 power cable (country-specific)
- 4 × rubber feet (for desktop/shelf placement without rack ears)
- 1 × printed Quick Start card
The RM99 rack-mount bracket is sold separately. If you intend to rack-mount the RELO IO8, order the RM99 before installation.
Front panel overview
The front panel carries the power button and LED indicators. From left to right: the recessed power button, the PWR status LED (green when powered), the NET LED (amber = link, blinking = activity), and eight numbered relay-status LEDs (one per relay, green when energised). The front panel also exposes the USB-A service port used for local configuration and firmware recovery.
Rear panel overview
The rear panel carries all field-wiring connections. From left to right: the IEC C14 AC input, the RJ-45 Ethernet port, the DB-9 RS-232 serial port, the relay output terminal blocks (OUT 1–8), and the digital input terminal blocks (IN 1–8). Each relay output block also exposes the COM (common), NO (normally open), and NC (normally closed) contacts.
Relay output wiring
Each relay output is a SPDT (single-pole double-throw) contact rated for 10 A at 250 V AC. Wire the COM terminal to the supply side, NO to the load when you want the circuit to be open by default, or NC if you want the circuit to be closed by default. Do not exceed the contact rating. Use an external contactor for high-current loads.
Digital input wiring
Digital inputs detect dry-contact closures. Connect one side of your switch or sensor to an IN terminal and the other to the adjacent GND terminal. No external voltage source is required. The RELO IO8 supplies a 3.3 V pull-up internally. Inputs are isolated and compatible with standard momentary pushbuttons, toggle switches, PIR sensors with relay outputs, and similar devices.
Maximum cable length for digital inputs is 50 m with standard unshielded cable. For longer runs, use shielded cable and connect the shield to GND at the device end only.