Importance

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Abstract

A single master unit hold circuit which can be utilized for a single or a group of telephone instruments connected to a common telephone line. A single latching circuit is coupled to the telephone line. The establishment of the hold condition may be affected in the off-hook state of the telephone instrument. Each of the telephones of the group has associated signaling capability. Each telephone can generate an actuating signal directly onto the telephone line, which is then detected by the latching circuit, and in response thereto a hold condition is placed on the telephone line. The hold condition is affected via the telephone line, by a momentary actuation of a control circuit common to the hold circuit and the control circuit; the control circuit being a part of the telephone instrument call-out circuit network. The signaling can be accomplished by the rotary dial on a dial phone instrument or by the push button pad on an instrument sold under the trademark Touch-Tone, or by means of other types of frequency generating devices. The hold condition is initiated and established while the phone instrument is in its off-hook state. Moreover, the active telephone instrument continues to remain in its voice communication state, the hold condition having been established, not withstanding, as long as the telephone receiver is not placed on-hook. A key feature of the invention is that the off-hook state and/or voice transmission state of the telephone instrument constitutes the decisive conduit or channel by which the control circuit can activate the hold circuit. The hold circuit cannot readily become activated when the telephone receiver (handset) is in the on-hook state.

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First Claim