Serial Hardware Flow Control True or False: Before sending data, a modem asserts the RTS (Request To Send) signal.

Introduction / Context:
Hardware flow control on RS-232 links uses handshake signals to coordinate transmission between a Data Terminal Equipment (DTE, typically the computer) and Data Communication Equipment (DCE, typically the modem). Distinguishing which side asserts which signal prevents miswiring and configuration errors.

Given Data / Assumptions:

• Standard RS-232 naming: RTS = Request To Send; CTS = Clear To Send.
• DTE is the initiator of RTS; DCE responds with CTS.
• We consider classic modem connections, not null-modem special cases.

Concept / Approach:

In RS-232, the computer (DTE) raises RTS to request permission to transmit. The modem (DCE) asserts CTS when it is ready to accept the data. Therefore, the statement “a modem sends RTS” in advance of transmission is false; the modem responds with CTS rather than initiating with RTS.

Step-by-Step Solution:

Verification / Alternative check:

Serial cable pinouts and modem AT command guides list CTS as a modem output and RTS as a DTE output, confirming the direction of control.

Why Other Options Are Wrong:

“True” would invert the signal roles. Blank or unspecified options are irrelevant.

Common Pitfalls:

Confusing hardware flow control (RTS/CTS) with software flow control (XON/XOFF), or mixing DTE/DCE terminology.

Final Answer:

False