Medflyer
Just to add to the always knowledgable silberfuchs. It is my understanding that EPR is more or less a direct indication of thrust whereas N1 is only the rotational speed of one component of the engine. However when setting EPR it is good to have an N1 indication to ensure EPR is being set within the defined rotational limits of the low pressure compressor N1. This can be highlighted by looking at the Air Florida crash into the Patomac River. The Capt used reverse to power back from the gate, in doing so ingesting snow into the engine freezing the EPR probes. On the take-off roll EPR was set however as noted by the co-pilot N1 was indicating low. He chose to ignore the indication with disasterous results.