Method and apparatus for determining the origin of a remote alarm indication signal

A network interface unit for determining whether an alarm originated within customer premises equipment or network equipment within a telecommunication system, including:

• (a) first receiver for receiving a first signal from a network;
• (b) first means, coupled to the first receiver, for determining whether the first signal is in an alarm state;
• (c) second receiver for receiving a second signal from a customer premises equipment;
• (d) second means, coupled to the second receiver, for determining whether the second signal is an indication that the signal received by the customer premises equipment from the network interface unit is in an alarm state;
• (e) third means, coupled to the second means, for generating a third signal, the third signal being an extended superframe format signal in which for a period of 90 milliseconds every 1.08 seconds an unscheduled message "0000 0000 1111 1111" in a data link, in which the right most bit is transmitted first, is replaced with a message "0011 1110 1111 1111";
• (f) transmitter for sending from the network interface unit a third signal to the network, the third signal being an extended superframe format signal in which for a period of 90 milliseconds every 1.08 seconds, the unscheduled message "0000 0000 1111 1111" in the data link, which is transmitted from with the right most bit being transmitted first, is replaced with a message "0011 1110 1111 1111" to indicate that the alarm indicated by the alarm state originated within the customer premises equipment, if the first signal is not in an alarm state and the second signal indicates that the signal received from the network interface unit is in an alarm state.

A method for determining the origin of an alarm within a telecommunication system, including the steps of:

• (a) receiving at a network interface unit a first signal from a network;
• (b) determining whether the first signal is in an alarm state;
• (c) transmitting from the network interface unit a second signal to customer premises equipment;
• (d) receiving a third signal at the network interface unit from customer premises equipment;
• (e) determining whether the third signal is an indication that the second signal received by the customer premises equipment from the network interface unit is in an alarm state;
• (f) if the first signal is in an alarm state, then transmitting from the network interface unit to the network a fourth signal which indicates that the signal received by the customer premises equipment is in an alarm state;
• and
• (g) if the first signal is not in an alarm state and the third signal indicates that the second signal is in an alarm state, then sending from the network interface unit a fifth signal to the network;
• wherein the fifth signal is composed such that equipment specifically designed to detect the fifth signal as distinct from the fourth signal, so detects the fifth signal, and equipment not specifically designed to detect the fifth signal as distinct from the fourth signal detects the fifth signal as being the same as the fourth signal, such that specially designed equipment can distinguish between an alarm state that originates at the network and at the customer premises without disrupting the ability of equipment not specifically designed to detect the fifth signal from determining that an alarm state exists on one of the legs of the telecommunication system upstream of the customer premises equipment in response to receipt of the fifth signal.