Figure 14: Receive Timing Without Soft Carrier Turn-Off; Figure 15: Receive Timing With Soft Carrier Turn-Off - Bell 5902 Hardware Manual

RF Carrier
Detect (RCD)
Received
Signal
Carrier Detect
(DCD)
Received
Data
Sequence of Operation
1. Sender keys radio and begins transmitting carrier.
2. Carrier is received after radio key-up and propagation delays.
3. Carrier detect delay starts timing at carrier reception.
4. Sender starts transmitting data after its RTS/CTS delay.
5. Carrier Detect (CD) must be true before data reception.
6. CD goes false after expiration of carrier loss delay.
7. False character might be received here due to sudden carrier turnoff. Modem
is ready for next reception or transmission.

Figure 14: Receive Timing without Soft Carrier Turn-off

RF Carrier
Detect (RCD)
Received
Signal
Carrier Detect
(DCD)
Received
Data
Sequence of Operation
1. Sender keys radio and begins transmitting carrier.
2. Carrier is received after radio key-up and propagation delays.
3. Carrier detect delay starts timing at carrier reception.
4. Sender starts transmitting data after its RTS/CTS delay.
5. Carrier Detect (CD) must be true before data reception.
6. CD goes false 4-10 ms after SCT tone starts. Receiver is disabled. No false
data is received since receiver is disabled before carrier turnoff.
7. Ready for next reception or transmission upon loss of received carrier.

Figure 15: Receive Timing with Soft Carrier Turn-off

5902 Bell 202 Modem Hardware Manual
October 19, 2007
(1)
(4)
(2)
marks
(5)
(3)
(1)
(4)
(2)
marks data
(5)
(3)
data
(6)
(7)
SCT
(8)
tone
(6)
(7)
25