QSIG supports which of the following ISDN supplementary services?

QSIG, which stands for Q Signaling Protocol, is primarily used for signaling in private branch exchange (PBX) systems. One of the key supplementary services that QSIG supports is call transfer. This service allows users to transfer an ongoing call to another extension or phone line within a network seamlessly, making it a crucial function for enhancing communication efficiency in businesses.

Call transfer is particularly relevant in environments where customer service and communication management are essential, allowing for the rerouting of calls to the appropriate personnel without requiring the caller to hang up and dial again. This functionality demonstrates the strength of QSIG in facilitating advanced call handling that is vital for modern telecommunications.

While voicemail access, intercom systems, and fax transmission are also important services in telecommunications, they do not fall under the specific supplementary services supported by QSIG. Voicemail access typically relies on different systems that manage messages, intercom systems may involve different technology for internal communication, and fax transmission relies on data protocols that are separate from the QSIG protocol.