The DSVD Modem

The Advantages of Digital SVD Digital SVD improves upon other simultaneous voice and data technologies in the following areas: Speed - Digital SVD offers simultaneous voice and data over newer, 28.8 kbps modems. While talking in Digital SVD mode, modem applications can typically run at 19.2 kbps data rates. Product Compatibility - Digital SVD is an open standard developed by leaders in the PC-modem industry to ensure that products from different companies will interoperate. Digital SVD modems will also work with the installed base of PC-modem applications. Digital Scalability - The all digital solution allows the future addition of newer modem technology, advanced voice compression and the ability for video transmission while still providing compatibility for voice and data communications. Digital SVD Application Examples Let's consider two computer game enthusiasts. One wants to know if the other would like to play a game, so he calls her on the telephone. She answers her telephone and accepts the invitation. Without disconnecting the conversation, they connect their computers over the data channel. They now interact with each other in the computer game, using the data channel, while talking over the voice channel. When they finish playing, they either exit the game, or select the hang up option without disconnecting the conversation. They hang up after finishing their conversation. Consider a customer tech support question for a software application. The customer calls the vendor using the voice channel. The vendor discusses the issue with the customer until the issue is understood and informs the customer that a driver update is needed. Since both parties have DSVD modems, the update is transmitted directly to the customer over the data channel while they remain on the voice channel. The customer continues to receive phone support while installing the new driver and making sure it works. They hang up after the customer's issue is resolved. These examples show how easy it is to use DSVD modems and how game play is enhanced with voice. The only thing that the developer provides is an initialization string, just like any other modem. Since voice is completely handled through the RJ-11 jack on the back of the modem, nothing needs to be done to the software to add voice. One Easy Setup A software application is Digital SVD-ready when the user can select the Digital SVD modem type from a setup menu. This occurs using a data file that is accessed through a user interface using the following steps: In the software application's setup options, the user selects the modem setup. The user selects a Digital SVD modem. The software application issues the correct initialization string to the modem. The initialization string typically goes to the modem each time the software application is run. The Initialization String The initialization strings for the U.S. Robotics 28.8 Digital SVD modem and the Rockwell 28.8 Digital SVD modem are: USR 28.8 Digital DSVD AT&F1-SSE=1 Rockwell 28.8 Digital DSVD ATQ0E1V1-SSE=1 These initialization strings are only intended for their respective modems. If a user places a different modem in the computer, then a different initialization string must be selected. If the Digital SVD Modem initialization string is used as a default initialization string for another modem, the other modem does not recognize the -SSE=1 Digital SVD Modem command and sends an ERROR result code back to the software. Working with Digital SVD Voice and Data The modems are disconnected only when both the voice and data are disconnected. When used simultaneously, 9.6 Kbps are dedicated to voice channel and 19.2 Kbps are dedicated to data channel. If one user hangs up the handset, then data transmits at the maximum bandwidth. The Digital SVD modem that is not using voice, functions as a normal V.34 28.8 Kbps data modem. In the examples above, the data connection is opened and closed without disconnecting the voice connection. The opposite is also true. That is, the handset can be picked up or set down as many times as desired during the session without disconnecting the data connection. Connecting to Other Modems When Digital SVD is enabled on the original modem and Digital SVD is not supported on the answering modem, the modem proceeds with a standard, non SVD, V.34 startup sequence. A standard V.34 connection with V.42bis compression and V.42 error control is established, if possible. If V.34 is not supported by the remote modem, the software tries to connect at lower bit rates such as V.32 and V.32bis. Voice Connection Tones When a handset is picked up, a low-high tone is sent across the voice channel to signify the transition from data-only to Digital SVD mode. When a handset is placed on-hook, a high-low tone is sent across the voice channel, to signify the transition from Digital SVD to a data-only connection. Two users can increase data rates to the maximum bandwidth of 28.8Kbps by simply hanging up one handset. The remaining user hears the high-low tone if their handset remains off-hook. If the handset is picked back up, the user is notified by the low-high tone, to signify the transition back to Digital SVD. Common Questions Q: Can you output the Digital SVD-decoded voice to the Soundblaster (digitally)? A: The only mapping of the Digital SAD Audio is out through the RJ-11 phone jack. No connection to a Soundblaster is provided. Q: How tolerant is Digital SVD to line noise? A: Line noise tolerance is a function of the V.34 protocol. The Digital SVD connection seems no more susceptible to line noise than any other V.34 modem. Q: Can you output Digital SVD-decoded voice to the hard drive or filter voice data on the host before encoding it on the modem? A: It is not possible today because current modems map voice to RJ-11 phone jacks. There is nothing in the DSVD specification that prevents this from happening in future implementations. When DSVD is implemented through a software solution, as envisioned in Intel's Native Signal Processing or NSP specification, this will be possible. Q: Can you control how much of the bandwidth gets allocated to voice or data? A: The only way is by hanging up the handset. This allocates maximum bandwidth to the data channel. Other References For further information, download the Digital Simultaneous Voice and Data Protocol Specification The spec is also available by calling the information line at 503-696-6070. Other brands and names are property of their respective owners. The URL of this document is: http://www.intel.com/pc-supp/multimed/other/dsvd.htm