Test Your EQ (Engineering Quotient)

EQ #64

Can you name all of the signals in the original 25-pin RS-232 connector?

What is the actual circuit? Draw a diagram of the circuit and indicate the required value of each voltage source.

Pins 9, 10, 11, 18 and 25 are unassigned/reserved. The rest are:

Pin Abbreviation      Source  Description
1   PG        —         Protective Ground
2   TD        DTE      Transmitted Data
3   RD        DCE      Received Data
4   RTS      DTE      Request to Send
5   CTS      DCE      Clear to Send
6   DSR      DCE      Protective Ground
7   SG        —         Signal Ground
8   CD        DCE      Carrier Detect
12 SCD      DCE      Secondary Carrier Detect
13 SCTS    DCE      Secondary Clear to Send
14 STD      DTE      Secondary Transmitted Data
15 TC        DCE      Transmitter Clock
16 SRD      DCE      Secondary Received Data
17 RC        DCE      Receiver Clock
19 SRTS    DTE      Secondary Request to Send
20 DTR      DTE      Data Terminal Ready
21 SQ        DCE      Signal Quality
22 RI         DCE      Ring Indicator
23 —         DTE      Data Rate Selector
24 ETC      DTE      External Transmitter Clock

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EQ #64

by Circuit Cellar Staff time to read: 2 min