What device can I use to parallel 4 dry contact signals from 4 timer relays
simulate this circuit &ndash; Schematic created using CircuitLab
Figure 1. All relay contacts are wired in OR configuration. Any one turning on will energise the solenoid vlave.
Note that this is not multiplexing which is generally a method by which multiple analog or digital signals are combined into one signal over a shared medium with the intention of extracting the original individual signals at the far end.