There was no other mu'adhdhin of the Messenger of Allah ﷺ. He then narrated the tradition which is incomplete.
أَخْبَرَهُ قَالَ وَلَمْ يَكُنْ لِرَسُولِ اللَّهِ ﷺ غَيْرُ مُؤَذِّنٍ وَاحِدٍ وَسَاقَ هَذَا الْحَدِيثَ وَلَيْسَ بِتَمَامِهِ
There was no other mu'adhdhin of the Messenger of Allah ﷺ. He then narrated the tradition which is incomplete.
أَخْبَرَهُ قَالَ وَلَمْ يَكُنْ لِرَسُولِ اللَّهِ ﷺ غَيْرُ مُؤَذِّنٍ وَاحِدٍ وَسَاقَ هَذَا الْحَدِيثَ وَلَيْسَ بِتَمَامِهِ