RSD-1 Digital Sharing device from RAD
The RSD-1 Digital Sharing Device enables up to 4 modems or terminals to share a master modem, a multiplexer or a computer port in a multipoint environment. The RAD RSD-1 is compatible with asynchronous or synchronous equipment at data rates up to 19.2 kbps.
Three clock modes are supported with the RAD RSD-1:
External from the main channel
External from subchannel 1.
A built-in buffer in the RSD-1 overcomes possible phase differences between the RSD-1 main channel transmit clock and the clocks of modems connected to the subchannels.
A DCE/DTE switch for main channel and each subchannel allows setting the channelís interface as DCE or DTE.
The main channel of the RSD-1 broadcasts to all subchannels in parallel. Subchannels contend to transmit to the main channel by activating RTS/DCD or by data transitions (strap-selectable). If the RTS/DCD is active or data transitions occur on a subchannel, its transmit data and control signals are connected to the main channel. When RTS/DCD drops or data transitions stop, the control circuitry is switched to monitor
other subchannels. A subchannel is disconnected immediately after it drops RTS/DCD or transmits 15 idle bits.
On the RSD-1, a subchannel can be disabled by automatic circuitry if it stays active for longer than a preset time, blocking all other subchannels (streaming). The automatic disable resets itself as soon as the subchannel RTS/DCD drops, or 15 idle bits are transmitted (Data Contention). Individual subchannel indicators on the front panel indicate if a subchannel was disabled by automatic circuitry. Manual disabling of a subchannel is also enabled via individual subchannel switches.
RSD-1 is available as a desktop unit or as a rack-mount card for the RSD-MN-12 rack. The rack can carry up to 12 RSD-1 cards and is supplied with 64-pin connectors. One or two power transformers are installed inside the rack providing hot standby backup.
RSD-1 product data sheet (pdf)