Specifications

Operation PSM-500/500L/500LT SCPC Satellite Modem
Page 3-42 PSM-500/500L/500LT - Rev. 0.91
2. The modulator responds to the DTE device when ready to transmit by activating the
CTS signal.
3. Any time after the CTS is received by the DTE, the DTE starts transmitting flags
and/or data. The first non–SDLC/HDLC flag character received by the modulator is
the start of transmission signal, causing the modem to generate a preamble and
initiate the “Carrier ON” command. Transmission continues with data bytes placed
after the preamble.
4. The next SDLC/HDLC flag received by the modulator is the end of transmission
signal.
5. When the closing flag is detected by the modulator, it drops the CTS indicating that a
new data message cannot be started. When the last data bit is sent, the modulator
will reassert the CTS signal, and turn the carrier OFF.