Apple GeoPort Telecom Adapter Kit - Manual (Page 73)

digital signal A discrete or discontinuous signal; one
whose various states are discrete intervals apart. Compare
with analog transmission.
digital to analog converter A device that converts data
from digital to analog form.
duplex transmission Two-way transmission.
E
echo To send a signal back to the originating device for
display or verification.
error code A number or other symbol representing a type
of error.
error control A process that analyzes data blocks and
calculates information about their content. The resulting
error-control information is transmitted with the data so that
the remote computer can verify data integrity.
error correction mode (ECM) A software protocol for
error correction used for fax transmission and reception.
ECM is helpful when telephone line quality is poor, but it is
not supported by most older fax machines.
error message A message displayed or printed to notify
the user of an error or problem in the execution of a
program.
even parity Use of an extra bit set to 0 or 1 as necessary
to make an even number of 1 bits in a character. For
example, the 7-bit ASCII code for the letter A (1000001) has
two 1 bits; for even parity, the transmitting device appends
an eighth bit equal to 0 so that the total number of 1 bits
remains even (01000001). The receiving device can count
the bits as a way of checking for transmission errors.
73 Glossary