CONTENTS

 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