Is it a condition for the validity of congregational prayer at work to have both the Adhan and Iqamah, or only the Iqamah?

The Adhan (call to prayer) for the congregation is desirable (mustahabb) to inform them of the entry of the prayer time and to alert them to prepare for it, and for the great reward it entails. The desirability of the Adhan for an individual has been used as evidence for its priority for the congregation. The Adhan is not a condition for the validity of the prayer; rather, it is a Sunnah or desirable act, and the prayer is not invalidated by its omission.