[Home](./index.md) > [sip.js](./sip.js.md) > [UserAgentCore](./sip.js.useragentcore.md) > [(constructor)](./sip.js.useragentcore._constructor_.md) ## UserAgentCore.(constructor) Constructor. Signature: ```typescript constructor(configuration: UserAgentCoreConfiguration, delegate?: UserAgentCoreDelegate); ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | configuration | UserAgentCoreConfiguration | Configuration. | | delegate | UserAgentCoreDelegate | Delegate. |