What was the charge (name and section number)?
Does it say NOTICE OF OFFENCE at the top of the ticket or SUMMONS?
I recommend you plead Not Guilty and request a Trial with officer present. Once you get your notice of trial with the trial date, then you can request disclosure (officers notes, speed measuring device manual). Once you get the disclosure notes, post them here so we can advise further.
There is no disadvantage to pleading not guilty as you can just pay the fine any time up until the trial date. The advantage of pleading not guilty is you get to review the evidence they have against you before deciding what to do.
+++ This is not legal advice, only my opinion +++