NJC = National Joint Council for local government services.
Instead of having separate salary systems for teaching assistants, finance office workers, or for the heads of major council departments, many council posts are allocated a 'spinal column point' on a common pay scale.
Because the lowest points were merged together in a prevoius pay settlement, the lowest 'spinal column point' is now numbered '4' (rather than '1'). So, someone accepting an NJC-scale position, at the bottom of the ladder, with no experience or special rsponsibilities to boost their pay, would be at 'SCP4', for which the annual salary is currently �11,193.
The term 'NJC Scale', in a job description, is, on its own, rather meaningless. You really need to know the relevant spinal column point(s). (e.g. the job you're applying for might be SCPs 4 to 8. That would mean that, unless you had previous relevant experience, you would start at SCP4 but then progress one point higher for each of the following 4 years before finally remaining on SCP8).
http://www.nyfvo.org.uk/info/payscales/njcpay2 006_07.pdf
Without knowledge of the relevant SCP(s), all that can safely be said about the salary is that (unless its a part-time or other 'pro rata' post) the annual salary must be at least �11,193.
Chris