The Confer II detects ringing signals on a line and answers that line. To release a line when a party hangs up, the Confer II requires disconnect from the line (the PBX or CO.) The preferred method is to see loop current interrupt on the line when the calling part hangs up, much like many voice-mail systems require. This is provided by virtually all COs and by most PBXs (except Northern Telecom). It may require a "voice mail" card or an OPX card in the PBX.

If a loop-current-interrupt is not provided, the Confer II can be set (by switch selection) to disconnect when North American is present on the line. This is the method used on any Northern Telecom PBX, plus others, and the PBX typically must be programmed to provide dial tone to the Confer II when the caller hangs up. There is a minor hazard in using dial-tone detection in the occasionally a participant's voice may sound like dial tone and the participant may be disconnected while talking. While the bridge has been designed to minimize this hazard, there remains about one percent chance that it will occur.

A third, default, disconnect is available (switch selectable) if no disconnect supervision is provided. It requires that a line remain silent after the caller hangs up. The bridge will release all lines after two minutes of silence is determined in the conference. There may be a problem in depending on this method if "coffee breaks" are taken during a long conference call. Steps must be taken to assure that some sound is "heard" by the bridge during the break, to avoid releasing all the lines. As stated, this is a last-resort to releasing lines at the end of a conference.