Sources generate the data that flows through the signal processing pipeline. This data can either be continuous (e.g., LFP) or event-based (e.g. TTLs, spikes).
The number of continuous outputs for a given source determines the number of channels for the rest of the signal chain, unless multiple sources are combined using as "Merger."
Sources can receive data from an external device, a local file, or a network connection, or generate it from scratch.