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davesparks
NO They Aint series is L or Pos to L or Pos as in series parallel circuits
search series parallel circuits - Bing - https://www.bing.com/search?q=series+parallel+circuits&form=EDNTHT&mkt=en-gb&httpsmsn=1&plvar=0&refig=82d61db8e9b34dc2df9f03016b336c02&PC=HCTS&sp=1&qs=AS&pq=series+parallel&sc=8-15&cvid=82d61db8e9b34dc2df9f03016b336c02&cc=GB&setlang=en-GB
From your link:
"Components connected in series are connected along a single conductive path, so the same current flows through all of the components"
With RCDs in series the same current flows through both devices (assuming nothing is branched off in between the). They are connected along a single conductive path, but having two poles they are each connected to two different parts of the same conductive path.