How did FBI negotiators communicate with David Koresh during the Waco siege?

During the 51-day siege of the Mount Carmel compound, FBI hostage negotiators communicated with David Koresh primarily through telephone calls.1

During these interactions, Koresh frequently engaged in what was described as "Bible babble" and issued threats of violence, though he maintained that neither he nor his followers were suicidal. These negotiations were used as a channel to facilitate the release of some followers; for instance, Koresh allowed more than 30 people to leave the compound, partly in exchange for supplies such as milk, which was delivered in cartons containing listening devices.1

Negotiations eventually stalled, particularly after Koresh failed to follow through on a promise to surrender if one of his sermons was broadcast on national radio. As talks faltered, the FBI employed various psychological and environmental tactics to pressure the group, including cutting off electricity, playing loud Tibetan chants, and using spotlights to disrupt sleep.1