CHAPTER 2: Introduction
2. Introduction
The Programmable Sharing Device enables up to 4 (TL304A) or 8 (TL305A) modems or terminals to share
a master modem, multiplexor, or computer port in an asynchronous or synchronous multipoint environment. (Asynchronous and synchronous equipment cannot be mixed on the same PSD.)
MAIN CHANNEL
The main channel transmits information to all sub-channels in parallel.
SUB-CHANNELS
Sub-channels contend to transmit to the main channel by activating RTS/DCD (Request to Send/Data Carrier Detect) or by data transitions (strap-selectable). When the sub-channel is active, the sub-channel’s transmit data and control signals are connected to the main channel. When RTS/DCD drops, data transitions stop, or 16 idle bits are received, the PSD will disconnect and monitor other sub-channels.
Sub-channels can be disabled either manually by front-panel pushbuttons or automatically. If a sub-channel
is streaming and staying active for longer than a configured amount of time, the PSD will automatically disable that sub-channel. A front-panel LED will illuminate to indicate that the sub-channel has been automatically disabled. The sub-channel will be reset when RTS/DCD drops or 16 idle bits are transmitted to it from the attached device.
CLOCK MODES
Three clock modes are supported: internal, external from the main channel, or external from sub-channel 1.
BUFFER
A built-in-buffer compensates for phase differences between the clocks of modems connected to the sub- channels and the PSD main-channel transmit clock.
An extra-buffer option on the PSD-8 can be activated when the PSD is connected to equipment that cannot accept an external clock. Examples include DDs (United States) or other digital lines and modems that cannot be set to an external clock. This additional buffer compensates for phase differences between the PSD clock and sub-channel clock(s).
RS-232 Cable
