AT and T designed one of the first commercial modems to convert digital computer data to analog signals for transmission over its long distance telephone network. What was the name of this historic modem?

Introduction / Context:
Before modern broadband and mobile data, early computers communicated over ordinary telephone lines using devices called modems, which modulate and demodulate signals. AT and T played a key role in commercialising these technologies. This question focuses on the specific name of one of the earliest standardized commercial modems developed for long distance communication over telephone networks.

Given Data / Assumptions:

• AT and T designed an early commercial modem.
• The modem converted digital data to analog signals for long distance phone lines.
• Options include Telex, Memex, CompuServe, and Bell 103 data set.
• We assume basic knowledge of telecommunication history and modem standards.

Concept / Approach:
The Bell 103 data set is widely recognized as one of the first commercial dial up modem standards introduced by AT and T in the early 1960s. It used frequency shift keying to transmit data at 300 bits per second over ordinary telephone lines. The other names in the options refer to different concepts: Telex is a teleprinter network, Memex is a hypothetical machine described in early hypertext literature, and CompuServe is an online service provider. Only Bell 103 directly matches the description of an AT and T commercial modem standard.

Step-by-Step Solution:
Step 1: Identify that the question is about a commercial modem created by AT and T for long distance network use.Step 2: Recall that Bell 103 was an early modem standard that defined how digital signals were modulated into analog tones for telephone lines.Step 3: Recognise that Telex was a network of teleprinters and not a specific modem standard.Step 4: Note that Memex was a conceptual information machine described by Vannevar Bush, not a real modem product.Step 5: Understand that CompuServe was an online information service rather than hardware for signal conversion. Therefore, Bell 103 data set modem is the correct answer.

Verification / Alternative check:
Historical documents on modem development frequently mention the Bell 103 standard as a milestone. Technical descriptions specify that Bell 103 operated at 300 bits per second and used different frequency pairs for sending and receiving data. These details are connected explicitly with AT and T and its Bell System research labs. Telex, Memex, and CompuServe appear in entirely different contexts and are not listed as modem standards.

Why Other Options Are Wrong:
Telex is a telegraphy style network where messages are typed on teleprinters and sent over dedicated lines; it is not the name of an AT and T modem. Memex is an early vision of a personal information workstation and has no direct connection to telephone modems. CompuServe was an online service provider that allowed subscribers to access information and email using modems, but it is the brand of a service, not the modem hardware itself. Thus these options do not satisfy the description given in the question.

Common Pitfalls:
Some candidates may be tempted by familiar sounding names like Telex or CompuServe without carefully analysing whether they refer to hardware or services. Another pitfall is confusion between network services and the devices used to connect to them. It is useful to remember that Bell numbered standards such as Bell 103 and Bell 212 describe modem technologies, while brand names like CompuServe identify service providers.

Final Answer:
The correct answer is Bell 103 data set modem, the early AT and T commercial modem standard that converted digital computer data into analog signals for long distance telephone networks.