I often see references to these phone plugs RJ9, RJ10, RJ22.
It turns out those are non-standard names for a 4P4C connector.
What are the people who use these names likely to mean?
Could they be using another name than 4P4C if the connector pins on the lead are wired in a certain way? (For example: outer and inner pairs, outer pair only, only pins 1 and 2, etc)
Could they be using a name based on the function which the lead performs? (For example: handset lead, recording adaptor lead, etc)