FP Modem-EU Technical Manual
7.1 Technical Terms
frequency modulation (FM, FSK), phase modulation (PM,PSK) and quadruple amplitude
modulation (QAM).
OFF HOOK
If the modem has answered, it is in ”Off Hook” state, i.e. the telephone line is occupied by the
modem and a connection to the telephone network has been established.
ON HOOK
If the modem has hung up, the connection to the telephone line has been terminated.
Operation mode
Two modes can be selected during a connection: data mode for sending and receiving data,
command mode for entering AT commands.
ORIGINATE
The calling modem enters ORIGINATE mode and the called modem enters ANSWER mode
while online data communication is carried out. See Answer mode.
PBX
Private branch exchange. Compare to PSTN.
Parity
Bit for asynchronous data transfer, serving for error detection. Part of the transmission format.
Sometimes omitted (no parity) or always one (mark) or zero (space). For even parity the bit is
set when the number of bits for the data is even. This works in an analog manner for odd parity
with an odd number of bits.
Protocol
Declaration on how to code or decode the signals or which data saving methods are used. One
differentiates between error correction and data saving protocols.
PSTN
PSTN stands for Public Switched Telephone Network (public telephone network). This is the
world wide voice telephone network that works with two wires.
Pulse dialing
Dialing using old telephones led to a series of impulses for the fixed pulse-width repetition rate.
With the ATDP command the modem also controls this dialing procedure, which is still required
by some telephone networks.
Remote data transmission
Remote data transmission between two data processing units that are separated
geographically from each other. Therefore two data lines are used. A data processing unit
sends its data via an interface to a dial-up networking unit (modem). There, the data are
processed and sent to the dial-up networking unit of the receiving data processing unit. Then
the data processing unit adjusts the signals for the receiving station.
Retrain
If the quality of the lines deteriorates significantly during transmission, both modems agree to
“retrain”. In this case, the lines transmission characteristics are analyzed anew and the
parameters adjusted accordingly. See also Autoretrain.
Ring
Ringing, signalling an incoming call.
RS232C
American EIA standard for serial interfaces. The international standard V.24 defines the
respective functional features; the standard V.28 defines the respective electrical features.
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