What technology is the standard method for converting analog telephone calls into digital data?

The standard method for converting analog telephone calls into digital data is Pulse Code Modulation (PCM). PCM works by sampling the amplitude of the analog signal at regular intervals and then quantifying these samples into a digital format. This process allows for accurate representation of the original voice signal in a digital format suitable for transmission over digital networks.

PCM is widely utilized in traditional telephony, VoIP, and other telecommunication systems because it efficiently uses bandwidth and maintains the quality of the voice signal. The sampling rate and bit depth used in PCM determine the fidelity of the audio, and it is the foundation for various audio and telecommunication codecs.

Other technologies mentioned, such as ASCII, deal primarily with character encoding for digital text and are not related to voice signal conversion. Internet Protocol (IP) is a network layer protocol used for routing and addressing packets of data, and Real-time Transport Protocol (RTP) is used for delivering audio and video over IP networks. While these protocols play essential roles in digital communications, they do not serve the specific function of converting analog audio into digital data as PCM does.