
Multiport for TNPP and TAP Outdial
134 025-9035AA
The number of nodes that may be directly connected to any given terminal is not limited
by the TNPP specification, but generally, vendors do not support direct connection with
more than eight other nodes.
There are two main modes of connecting TNPP nodes together. The simplex mode
consists of a single transmitter that sends TNPP data to one or more receiving nodes. The
simplex mode is limited to one way communications, the transmitting node only sends
data, and the receiving nodes only listen. The transmitting node can not be switched to be
a receiver. Simplex mode is usually used with a communications satellite link, with the
transmitting node being the uplink and each receiving node being supplied with a
downlink station in order to pick up the satellite's transmissions. Normally, simplex mode
uses the repeated transmission of a packet to insure that a packet is received correctly. The
TNPP protocol is designed to discard duplicated packets in order to avoid undesired
repetitions of a page.
Figure 30: Typical Simplex Distribution via Satellite
2000 Series Terminal
Sender
2000 Series Terminal
Receiver
Model 640 Terminal
Receiver
2000 Series Terminal
Receiver
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