Mishnayos Tamid Perek 5 Mishnah 6

The priest with the spoonful of incense and the priest with the gold coal pan filled with coals reached the place between the Entrance Hall to the Sanctuary and the outer altar, on their way to the Sanctuary. One of them took the shovel and threw it between the Entrance Hall and the outer altar. No person could hear the voice of another speaking to him in Jerusalem, due to the sound generated by the shovel. And that sound would serve three purposes: Any priest who hears its sound knows that his brethren the priests are entering to prostrate themselves in the Sanctuary at that time, and he would run and come to prostrate himself with them. And any Levite who hears its sound knows that his brethren the Levites are entering the courtyard to stand on their platform to recite the psalm accompanying the libation, and he would run and come to sing with them. And the head of the non-priestly watch, which stands in the courtyard as the agents of the Jewish people, would position the ritually impure priests and singers at the eastern gate of the courtyard, to make it clear that those priests were not performing the Temple service due to their ritual impurity.

הִגִּיעוּ בֵּין הָאוּלָם וְלַמִּזְבֵּחַ, נָטַל אֶחָד אֶת הַמַּגְרֵפָה וְזוֹרְקָהּ בֵּין הָאוּלָם וְלַמִּזְבֵּחַ. אֵין אָדָם שׁוֹמֵעַ קוֹל חֲבֵרוֹ בִּירוּשָׁלַיִם מִקּוֹל הַמַּגְרֵפָה. וּשְׁלשָׁה דְבָרִים הָיְתָה מְשַׁמֶּשֶׁת, כֹּהֵן שֶׁשּׁוֹמֵעַ אֶת קוֹלָהּ, יוֹדֵעַ שֶׁאֶחָיו הַכֹּהֲנִים נִכְנָסִים לְהִשְׁתַּחֲווֹת, וְהוּא רָץ וּבָא. וּבֶן לֵוִי שֶׁהוּא שׁוֹמֵעַ אֶת קוֹלָהּ, יוֹדֵעַ שֶׁאֶחָיו הַלְוִיִּם נִכְנָסִים לְדַבֵּר בַּשִּׁיר, וְהוּא רָץ וּבָא. וְרֹאשׁ הַמַּעֲמָד הָיָה מַעֲמִיד אֶת הַטְּמֵאִים בְּשַׁעַר הַמִּזְרָח: