921T Modem

Windows device driver information for 921T Modem

The device driver for the 921T Modem is a software application which is used to provide support to the communication device in order to support the implementation of the q.921 protocol. This type of communication protocol supported by the 921T Modem device driver is sometimes called the Link Access Protocol - D Channel (LAPD) which is closely associated with the HDLC. This protocol is the data link used for communicating over the D channel of ISDN networks. Essentially the process of transferring data can happen either via UI (Unnumbered Information) or I (Information) frames. In most instances UI is regarded as an unreliable form of delivery but is the simpler transfer method. This is primarily due to the elimination of the sequence numbering as well as the retransmission and acknowledgement requirements that are normally used in data exchange processes.

The I frames which is likewise supported by the device driver for the 921T modem on the other hand implements 128 numbered modules with the N(S) field containing the frame numbers required. In the same manner, the N(R) field is utilized as the holder for the acknowledgements between the communicating devices. In some instances it may be seen as piggybacking on the I frame in the opposite direction. There are also occurrences where it may be explicitly sent in either an RNR or RR frame. In this condition the RR frame means that the intended data recipient is ready and waiting for the transmission. The RNR status meanwhile means that a busy signal is being sent by the receiving party resulting in the data transmission packets being placed on hold within the circuit until an RR signal is received. It is highly recommended you run a free registry scan for and 921T Modem errors before installing any driver updates.