rate, transmitting an off-hook (answer) signal to the calling end. When the calling subscriber hangs up, disconnect timing starts (between 150 msec and 400 msec). After the timing is completed, SW1 and SW2 contacts are released in the calling switch. This opens the loop to the A relay in the called switch and releases the calling subscriber. The disconnect timing (150-400 msec) is started in the called switch as soon as the A relay releases. When the disconnect timing is completed, the following occur: If the called subscriber has returned to on-hook, SW3 contacts release. The called subscriber is now free to place another call. If the called subscriber is still off-hook, disconnect timing is started in the called switch. On the completion of the timing interval, SW3 contacts open. The called subscriber is then returned to dial tone. If the circuit is seized again from the calling switch during the disconnect timing, the disconnect timing is terminated and the called subscriber is returned to dial tone. The new call will be completed without interference from the previous call. When the called subscriber hangs up, the CS relay in the calling switch releases. Then the following occur: If the calling subscriber has also hung up, disconnection takes place as previ- ously described. If the calling subscriber is still off-hook, disconnect timing is started. On the com- pletion of the disconnect timing, SW1 and SW2 contacts are opened. This returns the calling subscriber to dial tone and releases the A relay in the called switch. The calling subscriber is free to place a new call at this time. After the disconnect tim- ing, the SW3 contacts are released, which releases the called subscriber. The called subscriber can place a new call at this time. REVIEW EXERCISES Give the three generic signaling functions, and explain the purpose of each. Differentiate between line signaling and interregister signaling. There are seven ways to transmit signaling information, one is frequency. Name five others. How does a switch know w