||God spoke to Moses, saying:
Vayedaber Adonay el-Moshe lemor.
||Make yourself two silver trumpets. Make them out of beaten metal. They shall be used by you to assemble the community and to make the camps break camp for their journeys.
Aseh lecha shtey chatsotserot kesef mikshah ta'aseh otam vehayu lecha lemikra ha'edah ulemasa et-hamachanot.
||When [both of the trumpets] are sounded with a long note, the entire community shall assemble at the Communion Tent entrance.
Vetake'u bahen veno'adu eleycha kol-ha'edah el-petach Ohel Mo'ed.
||If a long note is sounded on [only] one of them, the princes, who are leaders of thousands in Israel, shall come together to you.
Ve'im-be'achat yitka'u veno'adu eleycha hanesi'im rashey alfey Yisra'el.
Josephus describes them as a little less than one cubit (18') long, a little thicker than an ordinary flute, with a bell-like end (Antiquities 3:12:6).
See Exodus 25:18,31.