Identify the incorrect statement about common data communication components and control signals.

Introduction:
Many legacy and modern systems rely on standardized interfaces and control signals for serial communications. Knowing what each signal means and which protocols are synchronous vs. asynchronous helps avoid configuration errors. The question asks you to spot the one statement that is factually incorrect.

Given Data / Assumptions:

• Classical serial interface control uses signals like RTS (Request to Send) and CTS (Clear to Send).
• HDLC (High-Level Data Link Control) is a synchronous, bit-oriented Layer-2 protocol.
• Multiplexers combine multiple input streams for transmission over fewer physical lines.

Concept / Approach:
RTS/CTS implements handshaking for flow control: the DTE asserts RTS to request permission to transmit; the DCE responds with CTS to grant it. Ring indication is typically signaled by the RI (Ring Indicator) line in RS-232, not RTS/CTS.

Step-by-Step Solution:

Verification / Alternative check:
RS-232 pinouts explicitly list RI for ring detection; RTS and CTS serve flow control/handshake functions.

Why Other Options Are Wrong:

• Multiplexer statement: describes standard TDM/aggregate behavior.
• HDLC statement: reflects a well-known synchronous Layer-2 protocol.
• RTS/CTS readiness statement: aligns with DTE–DCE handshake usage.
• None of the above: false because one statement is indeed incorrect.

Common Pitfalls:
Mixing up RI with RTS/CTS; assuming all control signals are interchangeable.

Final Answer:
“RTS/CTS is the way the terminal indicates ringing” is incorrect.