There are three defined alarm indication signal states, identified by a legacy color scheme: red, yellow and blue.
AlarmsĪlarms are normally produced by the receiving terminal equipment when the framing is compromised. In all cases, the terminal equipment, i.e., the equipment that marks the endpoints of the DS1, defines the connection by the quality of the received framing pattern. In some cases, the connectivity may be lost in one direction and maintained in the other. Connectivity and alarmsĬonnectivity refers to the ability of the digital carrier to carry customer data from either end to the other. These two types of framing (SF, and ESF) use their 8 kbit/s framing channel in different ways. Due to the unique bit sequences exchanged, the framing schemes are not compatible with each other. A Super Frame consists of twelve consecutive 193-bit frames, whereas an Extended Super Frame consists of twenty-four consecutive 193-bit frames of data. Two types of framing schemes are Super Frame (SF) and Extended Super Frame (ESF). Because this 8-kbit/s channel is used by the transmitting equipment as overhead, only 1.536 Mbit/s is actually passed on to the user. This results in 8 kbit/s of framing data, for each DS1. Synchronization takes place by allocating a framing, or 193rd, bit. An additional 8 kbit/s of overhead is obtained from the placement of one framing bit, for a total of 1.544 Mbit/s, calculated as follows:įrame synchronization is necessary to identify the timeslots within each 24-channel frame.
This sampling is referred to as 8-kHz sampling (See Pulse-code modulation). A total of 1.536 Mbit/s of bandwidth is achieved by sampling each of the twenty-four 8-bit DS0s 8000 times per second. A DS1 is also a full-duplex circuit, which means the circuit transmits and receives 1.544 Mbit/s concurrently. A DS1 circuit is made up of twenty-four 8-bit channels (also known as timeslots or DS0s), each channel being a 64 kbit/s DS0 multiplexed carrier circuit.
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