1
Scope
1.1 Range of application
1.2 Applicable electrical
characteristics
1.3 Applicable mechanical
characteristics
1.4 Allocation of functionalities
2 Line of demarcation
3 Definitions of interchange
circuits
3.1 Circuit 102 Signal ground or
common return
3.2 Circuit 102a DTE common return
3.3 Circuit 102b DCE common return
3.4 Circuit 102c Common return
3.5 Circuit 103 Transmitted data
3.6 Circuit 104 Received data
3.7 Circuit 105 Request to send
3.8 Circuit 106 Ready for sending
3.9 Circuit 107 Data set ready
3.10 Circuit 108/1 Connect data set
to line
3.11 Circuit 108/2 Data terminal
ready
3.12 Circuit 109 Data channel
received line signal detector
3.13 Circuit 111 Data signalling rate
selector (DTE source)
3.14 Circuit 112 Data signalling rate
selector (DCE source)
3.15 Circuit 113 Transmitter signal
element timing (DTE source)
3.16 Circuit 114 Transmitter signal
element timing (DCE source)
3.17 Circuit 115 Receiver signal
element timing (DCE source)
3.18 Circuit 116/1 Back-up switching
in direct mode
3.19 Circuit 116/2 Back-up switching
in authorized mode
3.20 Circuit 117 Standby indicator
3.21 Circuit 118 Transmitted backward
channel data
3.22 Circuit 119 Received backward
channel data
3.23 Circuit 120 Transmit backward
channel line signal
3.24 Circuit 121 Backward channel
ready
3.25 Circuit 122 Backward channel
received line signal detector
3.26 Circuit 125 Calling indicator
3.27 Circuit 126 Select transmit
frequency
3.28 Circuit 128 Receiver signal
element timing (DTE source)
3.29 Circuit 131 Received character
timing (DCE source)
3.30 Circuit 133 Ready for receiving
3.31 Circuit 134 Received data
present
3.32 Circuit 135 Received energy
present
3.33 Circuit 137 - Transmitted character timing (DTE
source)
3.34 Circuit 138 - Transmitted character timing (DCE
source)
3.35 Circuit 140 Loopback/Maintenance
test
3.36 Circuit 141 Local loopback
3.37 Circuit 142 Test indicator
4 Operational requirements
4.1 Data circuits and timing circuits
4.1.1 Data circuits
4.1.2 Timing circuits
4.2 Control and indication circuits
4.2.1 Operation of circuits 107, 108/1 and 108/2
4.2.2 Circuit 125 - Calling indicator
4.2.3 Usage of circuit 126
4.2.4 Circuit 140 - Loopback/Maintenance Test
4.3 Miscellaneous
4.3.1 Interrelationship of circuits 103, 105 and 106
4.3.2 Idle periods
4.3.3 Clamping
4.4 Circuit failures (electrical)
4.5 Provision of interchange circuits
in DCEs and DTEs
4.6 Data flow control
4.7 Power-up considerations
5 References