 L-Carrier Transport Protocol System Bandwidth Capacity 3 MHz 1800 voice circuits 8 MHz 9300 voice circuits 17 MHz 32,400 voice circuits 57 MHz 108,000 voice circuits America is referred to as u-law, and the procedure used in Europe is referred to as A-law. The u-law and A-law are described in Sec. 18.1.2. The DS-0 channels are grouped together to form a DS-1 frame. The DS-1 frame tains 24 DS-0s and one framing bit, for 193 bits. DS-1 frames are transmitted at a rate of 8000 frames per second, as required to deliver the DS-0 samples at a rate of 8000 sample per second. The DS-1 frames are further grouped into groups of either 12 frames (a superframe) or 24 frames (an extended superframe). The sequence of 1s and Os assumed by the framing bit identifies both whether a superframe or extended su- perframe format is being used and where the first frame is in the transmission stream. The equipment receiving a DS-1 will examine the bits in each of the 193 bit positions until it detects the proper sequence of 1s and 0s. Once this is detected, the receiving equipment knows where the framing bits are in the bit pattern and proceeds to count off the frames in 193-bit chunks. Signaling information can be transported within each DS-0 channel by using technique called robbed-bit signaling. This technique is accomplished by overwriting the least significant bit in the DS-0 sample. It is not necessary to overwrite the least significant bit in every sample. Since the DS-0 is being transported within a DS-1 and the DS-1 has grouped the DS-1 frames into groups of 12 or 24, it is sufficient only to rob bits from a subset of the DS-0s. The practice used is to rob only the bits in the DS-0s transported in the sixth and twelfth frames of a superframe or, in the case of an extended superframe, the sixth, twelfth, eighteenth, and twenty-fourth frames. The approach used in Europe with E-Os is similar to that used for DS-0s. E-Os are grouped together to form an E-1. The data rate of the E-1 provides for thirty-two 64-kbps channels, but onl