what is an unconditional idhaar in tajweed rules

Question
what is an unconditional idhaar in tajweed rules
Answer
This is most likely referring to which we translate as absolute clearness.  This is when we have a saakinah and after one of the letters of the group of idhgaam letters () within one word.  We then pronounce the noon saakinah clearly.  This occurs in four words in the Qur'an: .   
Here we say the clearly even though it is followed by one of the letters of group because the occur next to each other in one word.  For the merging (idghaam) to take place, the has to be at the end of a word and one of the letters in the be the first letter of the next following word.