ADSL stands for Asymmetrical Digital Subscriber Line. It allows you to simultaneously access the net and use the phone or fax (at the same time). SDSL stands for Symmetrical Digital Subscriber Line. The difference between ADSL and SDSL is; ADSL has a different upstream and downstream data transfer rate (upstream higher than the downstream) whereas SDSL offers the customer a symmetric upstream and downstream bandwidth to the customer (eg. 1.5Mbps SDSL package offers the customer 1.5Mbps downstream speed as well as 1.5Mbps upstream speed). Technically, SDSL also does not allow voice/fax (PSTN) over the same copper.
http://www.streamyx.com.my/customer_care/c...stomer_care_faq