Telebit WorldBlazer User Manual page 56

DeE
Modem
Protective Ground
1
7
Si nal Ground
7
2
TO
TO
2
3
RO
RO
3
4
RTS RTS
4
5
CTS
CTS
5
OTR
OTR
20
20
6
OSR
OSR
6
Figure 8-2. Asynchronous Modified RS-232 Cable Diagram
Request to Send (RTS) and Clear to Send (CTS)
According to the RS-232 standard, the DTE asserts RTS
on pin 4 when it has data to transmit. It then waits for the
DCE to respond by asserting CTS on pin 5 before sending
data to the DCE via the TD line. Depending on its register
settings while operating in asynchronous mode, the
modem uses RTS and CTS to implement hardware flow
control between the DTE and the modem.
Data Terminal Ready (DTR) and Data Set Ready (DSR)
90257-01
the DTE uses pin 20 (data terminal ready) to indicate its
readiness to transmit or receive data. In automatic answer
mode, DTR is activated in response to the ring indicator
to tell the modem to answer the call. The DTR signal may
Interface Description 8-5