Using SPDT, SPST & Relay switches to control on/off of load. if more switches required, then more relays can be connected in series.
Applied example: Multiple switches in a long corridor controlling one load (e.g. lights, fan, etc.)
Note: DPDT switches may have been easier to wire (not provided as an option), so instead used 2 relays and 1 SPST switch to make an equivalent 1 DPDT switch.
