Figure 13: Transmit Timing With Soft Carrier Turnoff - Bell 5902 Hardware Manual

Received
Signal
CD LED
DCD
RTS
KEY
CTS
Transmit
Signal
Sequence of Operation
1. CD/DCD goes false 4-10 ms after receiving soft carrier turnoff tone.
2. DTE asserts RTS to transmit data. RTS is recognized when CD/DCD is false.
3. Carrier is turned on and radio is keyed 1-10 ms after SCT reception stops.
4. CTS is asserted by modem after expiration of RTS/CTS delay. Data transmission starts.
5. CTS is held true by modem and carrier continues to be transmitted for CTS hold time
after last character is transmitted and RTS returns to false.
6. Soft carrier turnoff tone is transmitted for SCT time.
7. Radio is de-keyed and SCT tone is turned off. Modem is ready for next reception or
transmission.

Figure 13: Transmit Timing with Soft Carrier Turnoff

5902 Bell 202 Modem Hardware Manual
October 19, 2007
SCT
Data
Tone
(1)
(2)
(3)
(4)
(5)
(6)
mark SCT
data
tone tone
(7)
24