Abstract: A two-path intercom system wherein a first link or path is non-exclusive and the second link or path is exclusive. When the system is idle, the first call is automatically switched to the second link or path when the called party answers. While the first conversation is taking place on an exclusive basis, a subsequent call will be switched to the first link or path, on a non-exclusive basis. The subsequent call is automatically switched to the exclusive second link or path when said second link or path becomes idle. The system includes a conference feature whereby tone dialing phones may switch up to three stations to the second link for a private conference. An intercom code not assigned to a station is used to set up the conference. A conference on the first link may be established when the second link is busy; when the second link becomes idle, the conference is automatically switched to the second link. In the idle state all stations are connected internally to the first link or path.

Abstract: A multiple link circuit for coupling a plurality of telephone lines to the ports of a port multiplexer without requiring the splitting of C-leads is disclosed. The multiple link circuit includes an internal priority determining arrangement that eliminates the need for individual links to be scanned by an address scanner. Each link of the multiple link circuit is bridge connected to a C-lead and includes: a busy detector for detecting the busy status of the C-lead; and, a control circuit for controlling the coupling of a subscriber seized telephone line to the associated port. The priority determining arrangement prevents any lower priority control circuit from coupling a seized telephone line to the associated port if any higher priority line is simultaneously attempting to be so coupled. After signal processing (performed by a signal processor connected to the port) has ended, or some other release action occurs, a port generated release signal disconnects the seizing link from the port.