Abstract: A circuit and method is described enabling a telephone having two or more lines to have the capability of initiating two simultaneous calls, where there is two-way communication on one of the calls (the collaborating call"), and active monitoring of the second call (the "teleconference"). A router is used so that the outbound audio signal of the user can easily be switched between the teleconference and the collaborating call. At all times, the transmit path of one of the calls is muted to ensure privacy of the other call.

Abstract: A circuit for use with a SCWID adjunct to remove A.C. in-band signaling tones from the voice path to a telephone apparatus serially connected to the adjunct. The A.C. signal component is carried on top of the D.C. voltage used to power the telephone. The circuit includes means to monitor the D.C. voltage level and to pass this voltage substantially unchanged to the telephone. The A.C. signal in the form of a FSK tone, received from the central office, is used by the adjunct to provide a subscriber with call feature information such as the identity of a calling party while the telephone is off-hook.