Quorum call

In the United States Congress, bells are rung in the various congressional office buildings to indicate to members that their presence is required in their respective chambers.

In fact, if any Senator "suggests the absence of a quorum", the Presiding Officer must direct the roll to be called.

[1][2] Because of differences in procedure between the two bodies, quorum calls in the House are fairly rare, but they are quite common in the Senate.

In both houses, while quorum calls officially last fifteen minutes, the actual amount of time given is at the discretion of the presiding officer.

Each House is expressly "authorized to compel the Attendance of absent Members, in such Manner, and under such Penalties as [it] may provide.