| 摘要 |
<p>A self-testing selection arrangement which may be employed in a communication switching system having a switching network responsive to marker-generated control signals supplied over a series of control connections, includes a sequence counter for controlling a connection selection apparatus, which in the preferred embodiment is a relay tree apparatus. During the selection of a control selection, the selection apparatus responds to the sequence counter for generating a signal indicative of a selected set of connections, and test circuits responsive to the signal to advance the counter, which in turn causes the selection apparatus to establish a selected one of the control connections. During a subsequent release of the selected established connection, the counter causes the selection apparatus to release the connection, and in response thereto, the counter is advanced. The signal indicative of the selected set is de-activated in response to the last-mentioned advancing of the counter, whereby during both the establishment of a connection and the releasing of it the counter is advanced only in response to the successful completion of each step of the operation and if any one step is not successfully completed due to malfunctioning of the equipment or for any other reason, the counter is not advanced and and a maintenance request for service is initiated.</p> |
