abort - to stop doing something. particularly, to exit a software program or stop receiving or sending a message.
access - (1) (verb) to get use of something, or (2) (noun) refers to a particular level or security clearance of use of something (i.e., one's "access" to the mainframe).
account - a term that refers to information that a particular telecom system has about you, and typically refers to an id number or your personal information.
ack - a character transmitted by a receiver that acknowledges that some particular reception took place.
acoustic coupler - this is an acoustic modem that transfers data over phone lines by tones and sounds instead of electronically. old-fashion handsets fit into a the modem to transmit information.
acoustic modem - this is simply a modem that uses an acoustic coupler.
adaptive dialing - a modem will try dialing with tones initially and will then dial in pulse if necessary (i.e., if tone dialing is ignored).
adc - this stands for analog-to-digital conversion.
adsl - this stands for asymmetrical digital subscriber line and is the typical dsl service that connects customers to the internet. preexisting channels in telephone lines are used to transmit data to and from the net.