In the phrase CCTV, closed circuit television; do we omit the -ed, and just say /kləʊz-sərkət-.../ in fast, connected speech. And, about the word "closed" itself, is it finished with an /zd/ or /st/ sound, when it comes alone?
The final -ed would be either omitted or reduced to a vestigial -t in normal speech. The elision between the /z/ and the /s/ can clearly be seen in this spectrum, where the vestigial t can (believe it or not) still be heard.
I believe that the technical term for this is an unreleased consonant: you can find more about it here.
In normal speech, the word is pronounced /kləʊzd/, as can be seen in this spectrum: