RS232 has been around for a long time. It works by setting the signals to either a mark (> 9V, typically 12V) and space (< -9V, typically -12V). As you can imagine this 24V swing is pretty noisy and can cause a lot of cross talk at higher speeds. That is why it typically does not go much faster than 128Kbps.
This has been modernized into the 9 pin com port on the PC and sometimes used on a RJ11 (phone jack).
Transmitted Data, TxD
Received Data, RxD
Request To Send
Clear To Send
Data Set Ready
Signal Ground, GND
Data Carrier Detect
Secondary Data Carrier Detect
Secondary Clear To Send
Secondary Transmitted Data
Transmission Signal Element Timing
Secondary Received Data
Receiver Signal Element Timing
Secondary Request To Send
Data Terminal Ready
Signal Quality Detector
Data Signal Rate Selector
Transmitter Signal Element Timing
UnBalanced RS232 (V.24)
The typical unbalanced driver is the standard RS232 1488 IC, however this requires + and - 12 Volts. Many of the new interfaces are using the V.24 / RS232 driver chips with the charge pump built in, so they only need +5V to operate. These come in many configuration some include both drivers and recievers. Two parts that come to mind is the DS14C232 from TI or Max 232.
UnBalanced RS232 (V.24) Receiver
The typical IC used for the reciever is the 1489, it only requires 5 volts to operate, but most new designs are using the charge pump IC which have both the receivers and drivers in the same chip.
RS232 Breakout, Testing and Conversion
ADVICE manufactures unique products for adapting RS232/V.24 to other standard interfaces:
The UMATS and Exchanger allow conversion between many types of interface: RS232 to V.35, RS449 or RS530.
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