RS232 Signaling (for modem outdial)

• DTR raised
• phone # dialed
• RNG on other end, if DTR (and auto-answer)
• DSR when answered
  
• RTS raised by DTE
• DCD is checked (bymodem) to see if far-end DTE has RTS high
• CTS raised if DCD/RTS is low
• transmit data lead (pin 2) from DTE
• receive data liead (pin 3) from DCE
• RTS dropped on completion of all data
• remote DCD drops
• CTS drops