Generally, when you use "functional equivalents" in a sentence, there is always a description about the function. In this case, the description of the "function equivalents" is "public relations". Therefore, I didn't repeat the conterpart "function" in my Chinese translation, since the function is already described as "public relations". From the text where phrase of functional equivalents appears, my understanding is that the equivalents could be a department or a personal. Above is the rationale behind my translation. Hope I get my point across.