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Collaboration, Voice & AV · Foundational

RS-232 Control

Serial control of AV devices over a DB9 or terminal connection using transmit, receive and ground conductors.

Definition

RS-232 sends ASCII or hexadecimal commands at a configured baud rate, commonly 9600 bps, 8 data bits, no parity and 1 stop bit (8N1). On a DB9 DTE connector, pin 2 is receive, pin 3 is transmit and pin 5 is ground; connecting two DTE devices requires a null-modem (crossed 2 and 3) cable. Typical maximum cable length is about 15 m (50 ft), and it provides two-way communication with feedback.

Example

A control processor sends PWR ON at 9600 8N1 to a projector's RS-232 port and reads back the lamp status.

Exam tip

When serial control fails, check baud rate, 8N1 settings and whether TX and RX need to be crossed.

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