�1���� Signalling types
�2����
Free line condition
�3����
Call
�4����
Call-confirmation signal
�5����
Signals preceding selection
������� 5.1���� Proceed-to-select signal
������� 5.2���� Proceed-to-transmit signal
�6����
Selection signals
�7����
Call-connected signal
�8����
Idle circuit condition
�9����
Clearing
������� 9.1���� Clearing signal
������� 9.2���� Clear-confirmation signal
������� 9.3���� Guard delay
10���� Service signals
������ 10.1���� Signals for ineffective calls
������ 10.2���� Waiting signals
������ 10.3���� Service-connected signal
������ 10.4���� Backward busying signal
������ 10.5���� Retest signal
11���� Setting-up time
12���� Both-way working
13���� Transit working
References