User's Manual

GLOSSARY
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© RF Innovations Pty Ltd, 1998 Page: 99
234839, Revision 2.2
Modem Eliminator
A usually passive device, which takes the place of a modem between a local terminal, which requires a modem, and a
computer. Also called Null Modem.
Modulate
To modify or alter a signal so as to transmit information. For example, conventional broadcast radio transmits sound by
modulating the amplitude or the frequency of a carrier signal. See also Demodulate and Modem.
Multiplex
To interleave or simultaneously transmit two or more messages on a single channel.
N
NAK
Negative Acknowledgment. This control character indicates that the last block transmitted was in error and that the receiver is
expecting a re-transmission.
Network Address
If the modem is a master, then this is the network identification number. Slaves are synchronised by the master that has the
same network address. A radio will ignore messages originating from radios with differing addresses. Must be the same for all
radios within a network.
Network Fail Timeout
The length of time that the system will wait after a signal is lost before trying to re-synchronise.
Network Identification Number
See Network Address
Node
A point of interconnection on a circuit.
Noise
Random electrical signals introduced by components of the circuit or natural disturbances that can produce errors in
transmission.
Non-Volatile Memory
Stores data/programs/configurations without the need for a battery backup. Will not be erased if there is a power failure.
Nearly permanent.
Null Modem
See Modem Eliminator.
O
Odd Parity
Odd parity refers to the appending of a 0 or 1 value bit to the data bits of a character to ensure that an odd number of 1-value
bits are sent. See also Even Parity and Parity.
Off-line
Describes the state of a connection as not in session or not currently connected. There is no communications link between
the modems, system has not dialed.
On-line
Describes the state of a connection as in session and currently connected. The system has dialed and a communications link
has been formed allowing the transfer of data. On-line LED on front of RFI-9256 is activated.
On-line Requests Timer
Controls the time between slave integrity checks by the master.
On-line State
When a Communications Link is established and dialogue is between your computer and a remote system. The local modem
assumes that all information from your computer is to be sent on to the remote modem. All AT commands are ignored by
the local modem but are acted upon by the remote modem. See also Local Command State.