+1A2 denotes a modular key telephone system, a foundational technology for business communications. Developed by the [Bell System](/wiki/Bell_System), it integrated multiple lines and features into a single [Telephone](/wiki/Telephone) unit, defining office connectivity for decades.
+## See also
+- [Key System](/wiki/Key_System)
+- [Telephony](/wiki/Telephony)
+- [Switchboard](/wiki/Switchboard)