| IMSI | International Mobile Subscriber Identity |
| TMSI | Temporary Mobile Subscriber Identity |
| IMEI | International Mobile Equipment Identifier/Identity |
| SIM | SIM-Karte [Subscriber Identity Module] |
| MMSI | Maritime Mobile Service Identity |
| MSE | Mobile Subscriber Equipment |
| ISIC | International Student Identity Card Association Hamburg, http://www.isic.de |
| IMT | International Mobile Telecommunications |
| CI | Corporate Identity |
| GID | Group IDentity |
| CII | Call Identity Index |
| EIR | Equipment Identity Register |
| LAI | Location Area Identity |
| DAMI | Direct Access to Molecular Identity |
| ESDI | European Security and Defence Identity |
| SN | Subscriber Number |
| SCM | Subscriber Carrier Module |
| OPSM | Outside Plant Subscriber Module |
| DSS | Digital Subscriber Signalling |
| DSL | Digital Subscriber Line |
| MSN | Multiple Subscriber Number |
| STD | Subscriber Trunk Dialing |
| ABS | Absent Subscriber [engl.] Teilnehmer nicht erreichbar [Telefon] |
| SNI | Subscriber Network Identifier / Interface |
| FDSL | Flexible Digital Subscriber Line |
| IDSL | ISDN Digital Subscriber Line |
| USIM | Universal Subscriber Identification Module |
| ASAM | ATM Subscriber Access Multiplexer [engl.] |
| EDSS | European Digital Subscriber System |
| EDSL | Ethernet Digital Subscriber Line |
| DSLB | Digital Subscriber Line Board |
| WDSL | Wireless Digital Subscriber Line |
| T-DSL | Telekom Digital Subscriber Line |
| RSLE | Remote Subscriber Line Equipment |
| RSLM | Remote Subscriber Line Module |
| SWING | Subscriber Wireless Network Gateway |
| ASDL | Asymmetric Digital Subscriber Line [engl.] Schnelle Datendienste über vorhandene Kupferkabel mit unterschiedlichen Datenraten in den beiden Übertragungsrichtungen |
| BDSL | Broadcast Digital Subscriber Line [engl.] Schneller Internetzugang über Rundfunkdienste |
| CCBS | Completion of Calls to Busy Subscriber [engl.] Telefon: Rückruf bei Besetzt |
| LDSL | Low Speed ISDN Digital Subscriber Line |
| DSLAM | Digital Subscriber Line Access Multiplexer |
| RDSL | Residential / Reverse Digital Subscriber Line |
| RADSL | Rate Adaptive Digital Subscriber Line |
| CDSL | Consumer Digital Subscriber Line [engl.] |
| MADSL | Margin Adaptive Digital Subscriber Line |
| HDSL | High rate Digital Subscriber Link |
| UDSL | Unidirectional / Universal Digital Subscriber Line |
| MDSL | Medium Bit Rate/Multirate Digital Subscriber Line |
| VDSL | Very High Data Rate Digital Subscriber Line |
| ADSL | Asymmetrical Digital Subscriber Line // Loop [engl.] Teilnehmer-Anschluss mittels Telefonkabel |