HDSL is a reletively new technology that is the next generation of DSL. Droit Technologies, Inc. was involved in a project to extend the Office PBX and LAN to a remote site. The office was just over a mile from the remote site. The HDSL modem chosen was the ADC Telecommunications Campus-RS Flex unit (formerly a Pairgain product). You need a Campus-RS Flex on each end. The Campus-RS Flex has two data ports, one of which was used to extend the Ethernet LAN from the office using RAD Tinybridge units. The Campus-RS Flex accepts a DSX-1 (T1 data rate) signal that normally has 24 voice grade digital channels. The remote location didn't need 24 channels, so 11 channels at 64KB/s per channel (704 KB/s) were dedicated to the Ethernet.
The RAD Tinybridge unit is also needed on each end and connected to the Campus-RS Flex data port with a ITU V.35 interface. There was some difficulty, initially, in figuring out what clock to use for each of the devices. ADC and RAD hadn't paired these particular pieces of equipment before. So the interface scenario is laid out as follows:
The scenario is Office PBX-to-Campus-to-Campus-to-Remote PBX, with the Tinybridges on the Data 1 port of the Campus-RS Flex.
For both RAD Tinybridge, the settings for the DIP switch is OFF for all switches.
For the Office Campus-RS Flex :
The primary timing is DSX-1; The Data Port 1 settings: V.35 Tx clock set to internal, The Control ports: CTS-STD; DSR-ON; RLSD-ON; LB-OFF
For the Remote Campus-RS Flex :
The primary timing is HDSL; The Data Port 1 settings: V.35 Tx clock set to internal, The Control ports: CTS-STD; DSR-ON; RLSD-ON; LB-OFF
For budgeting of the hardware, the Campus RS remote is approx. $700 each, RS Flex module (goes in the Campus Remote) are approx $290 each, and the RAD Tinybridges were about $700 for the pair - $2680. How many months of renting a T1 line to break even? You still need to stuff Ethernet into the T1, in the above scenario. It made sense for the customer.