Is it permissible for the muezzin to perform the adhan while sitting in front of the microphone if his health does not allow him to stand?

It is better for the muezzin to make the call to prayer (adhan) while standing. It is disliked for him to sit unless there is an excuse; however, with an excuse, it is not disliked. The scholars have unanimously agreed that the Sunnah is for the muezzin to make the adhan while standing. This is indicated by the Prophet's (peace and blessings be upon him) statement to Bilal: "Stand and make the adhan." If the muezzin has an excuse, then there is no harm in him making the adhan while sitting.