Ethernet to HSSI, RS-232, EIA-530, X.21, V.35, RS449/ V.36

The Metrodata LH1000 is designed to enable the transmission of LAN frames across satellite links via serial modems. The LAN interface is auto-sensing and supports 10M, 100M, full or half duplex working. Manual selection of 100BaseT FD operation enables connection to fixed config router ports. It is presented as an RJ45 connector and offers automatic MDI/MDI-X interface selection to obviate the need for cross-over cables. The LAN interface utilises an efficient HDLC encapsulation with address learning and filtering at up to 148810 packets per second. Rate decoupling is supported by means of a 1000 packet SDRAM buffer store, and no packets are lost providing that the sustained data rate is below the DTE serial port speed.

Front: LH1000 Ethernet to HSSI, RS232, EIA530, X21, V35, V36

Back: LH1000 Ethernet to HSSI, RS232, EIA530, X21, V35, V36

Two DTE ports are provided. They can operate at asymmetric speeds since they are clocked using the DCE supplied Send & Receive Timing signals. The ports are:

• a high speed HSSI DTE port using a standard 50-way SCSI-2 connector at a DCE clock rate of up to 100Mbps
• a low speed multi-standard port using a 44-way D-Type connector at clock rates up to 20Mbps

The low speed multi-standard port offers the options of RS-232, EIA-530, X.21, V.35, RS449/ V.36 interfaces, depending upon the type of interface cable fitted to the port.

HSSI Interfaces on Satellite Modems can go as high as 90Mbps, but typically HSSI is only used up to 51.84Mbps or STS-1. This is the "theoretical" maximum speed of HSSI (also known as EIA/TIA612). This is more down to Router HSSI Modules unable to go any faster than 52Mbps. The other problem with running HSSI at high speeds is that the line driving capability is drastically reduced the higher the data rate. Metrodata also offers an alternate product, the HE1000 which is a HSSI Extender and can provide HSSI extension up to 150m. With the LH1000 it is possible to support an Asymmetric Satellite service with HSSI used for the higher rate and EIA530 used for the lower rate. This can be a more cost effective solution than buying 2 x HSSI Satellite Modems.