Channel Associated Signalling Bits are bits dedicated for connection control across a 1544 kbit/s or 2048 kbit/s interface that carries 64 kbit/s channels. Procedures are based on the state of up to four signalling bits (A, B, C, D) that are allocated per channel per multiframe. See I.366.2 3.1.3.2/G.704 and 5.1.3.2/G.704. The service provided is the transfer of channel associated signalling information, i.e. the transfer of ABCD bits. Typically, the value of the (A,B,C,D) vector does not change for extended periods of time. Valid values are enabled and disabled. For jetstream atmVccAal2AppId the only valid value is disabled.