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| 2-D | 2-dimensional |
| 3-D | 3-dimensional |
| 3G | 3rd Generation mobile systems |
| 3GPP | 3rd Generation Partnership Project |
| ACL | Asynchronous Connectionless Link |
| ADC | Analogue to Digital Conversion or Converter |
| ADMD | After Diversity Maximum Demand |
| ADSL | Asymmetric Digital Subscriber Line |
| ADSS | All-Dielectric Self-Supporting |
| AES | Advanced Encryption Standard |
| AGC | Automatic Generation Control |
| AM | Automated Mapping |
| AMM | Automatic Meter Management |
| AMR | Automatic Meter Reading |
| ARIMA | Autoregressive Integrated Moving Average |
| ARIMAX | Autoregressive Integrated Moving Average with exogenous variables |
| ARMA | Autoregressive Moving Average |
| ARMAX | Autoregressive Moving Average with exogenous variables |
| ARPANET | Advanced Research Projects Agency Network |