This object specifies the forward signal indicating that the outgoing half echo suppressor has already been inserted and requesting that the incoming half echo suppressor also be engaged. Echo suppression on long-delay circuits works in two halves, one per direction, so this signal is specifically the handshake step that completes the pair, and if it is missed the call proceeds with only one direction's echo suppressed, leaving audible echo on the other leg. After inserting its own outgoing suppressor, the originating exchange sends this signal so the terminating exchange engages its incoming-half suppressor too, completing echo cancellation for both directions of the call.