Cone of Silence

The Cone of Silence is one of many recurring joke devices from Get Smart, an American comedy television series of the 1960s. In the series, whenever Maxwell Smart ("Agent 86") wanted to speak to his boss ("Chief") about a top secret matter, he would insist on the use of a comically defective technology called "the Cone of Silence." The Chief, usually with annoyed skepticism, would press a switch, causing the device to descend from above the Chief's desk, surrounding the heads of the two would-be conversers. The awkwardly impractical device was clear plastic in the shape of two interconnected inverted bowls. Part of the humor was in the irony that Agent 86 and Chief could never hear each other clearly, while bystanders in the room could hear everything they said. Often at the end of the labored conversation, the Chief would be terribly frustrated and upset.
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Synonym antenna blind cone.

An oath by a solicitor or other employee in a law firm not to disclose any information in regards to a previous client otherwise placing that lawyer or employee in a conflict of interest with other clients of the same law firm. - (read more on Cone of Silence)