[Home](./index.md) > [sip.js](./sip.js.md) > [UserAgentClient](./sip.js.useragentclient.md) > [(constructor)](./sip.js.useragentclient._constructor_.md) ## UserAgentClient.(constructor) Constructs a new instance of the `UserAgentClient` class Signature: ```typescript constructor(transactionConstructor: ClientTransactionConstructor, core: UserAgentCore, message: OutgoingRequestMessage, delegate?: OutgoingRequestDelegate | undefined); ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | transactionConstructor | ClientTransactionConstructor | | | core | UserAgentCore | | | message | OutgoingRequestMessage | | | delegate | OutgoingRequestDelegate | undefined | |