The pattern sent is 12 bits long, so every group of 12 frames is called a superframe.
It is preferred to its predecessor, superframe, because it includes a cyclic redundancy check (CRC) and 4000 bit/s channel capacity for a data link channel (used to pass out-of-band data between equipment.)
It requires less frequent synchronization than the earlier superframe format, and provides on-line, real-time monitoring of circuit capability and operating condition.
Like the predecessor superframe, every sixth frame's least-significant data bit can be used for robbed-bit signaling of call supervision state.
Unlike the superframe, it is possible to avoid robbed-bit signalling and send call supervision over the data link instead.