What type of output can directly power a relay?

An open collector output is designed in such a way that it can connect to a relay and effectively turn it on or off. This output works by allowing the device to pull the line low (grounded) when activated while being able to float high (unconnected), which is essential for controlling external components such as a relay. When the open collector output is activated, it closes the circuit to ground, allowing current to flow through the relay coil which is necessary for the relay to function.

In contrast, a closed collector output cannot be used to directly power a relay because it is normally in a low state (conducting) and wouldn't allow the relay to be controlled properly. Analog output is primarily used for varying signals and is not suitable for binary on/off operations like a relay requires. Digital output, while it does operate in a binary fashion (high or low), does not specifically indicate whether it is able to sink or source current in the way that a relay needs, as it depends on the configuration of the output circuit. Therefore, the open collector output is the most suitable option for directly powering a relay.