User's Manual

Page 173
8.11 Glossa ry of T erms
1:1, 1:n, n:m
Ratios indicating communication topology node architecture. The ratio 1:1 indicates a
system with only two nodes communicating with each other. The ratio 1:n indicates a
system with one “master” node communicating with a variable number of “slave”
nodes (also referred to as point-to-multipoint). The ratio n:m indicates a variable
number of nodes communicating with a variable number of other nodes.
ACK/NAK
In the packet transmission mode, a specific response is sent to the transmitting
modem to confirm the successful receipt of data, which is called ACK. In the
transmission through the repeater, the repeater sent a specific response to the
transmitting modem to convey that no ACK is returned from the destination modem
by the repeater, which is called NAK.
Antenna Diversity
A method commonly employed to improve the signal strength of received signals.
This method uses two independent antennas that receive signals differing in phase
and amplitude resulting a difference in the two antenna positions. Either the two
signals are summed or the strongest is accepted.
The method of checking transmitted data, used on virtually all high-speed data
communications systems. The sender encodes an error-detection field based on the
contents of the message and the receiver recalculates the field and compares it with
the one it received. If they match, an “ACK” (acknowledgement) is transmitted to the
sender. If they do not match, in some case, a “NAK” (negative acknowledgment) is
returned and the sender retransmits the message.
Asynchronous Communication
In this operation, the transmitting and receiving modems confirm the start and end of
1-byte data with the signal level (start bit and stop bit). As being simpler than the
synchronous system which requires to send the clock signal in addition to data, this
system is widely prevailing as the communication system of PCs. RS-232C interface
is originally the standard of the electric signal level, but actually it is called as the
asynchronous operation.
Bit
A contraction of the term “binary data”. A bit is the smallest unit of digital
information and is typically represented by a zero or one.
bps, or bits per second
The number of bits transferred per second.
Break Signal
One of a signal control signal. The data line (TxD/RxD) remains in the “Lo” state for
more than 1 byte (may be for several 100 ms). When data are sent in the
ARQ, or Automatic Retransmission Request
Futaba Corporation Rev. 020323-01