Voice Clipping ASP Print friendly page

Problem:

Voice switches have inherent call connect delays. In air traffic control switches these delays cause significant problems on “voice call” lines. A controller at one facility can push a button and immediately start talking to controllers at other facilities. If the receiving switch delays are more than 100-200 msecs part of message is lost. This is often referred to as "audio clipping".

In some switches the delays can be as much as 500 msecs. The delay depends on several factors, such as switch design and the amount of traffic that is being handled by the switch. The busier the switch the more likely the delay will increase.  

This situation can result in the loss of a word or part of a word – making it necessary for the receiver to guess what was said or ask for the message to be repeated. In many instances this can cause significant problems. In an air traffic control situation this adds to the work load of a very busy controller and potentially decreases safety.  

Solution

Digital Signal Products, Inc. has developed an Audio Signal Processor (ASP) that totally removes this problem. The processor is “transparent” to the switch and all other operations proceed normally. The following is a brief outline of how the ASP works:  

It monitors the receive lines for voice activity - speech energy is compared to idle channel noise to detect a valid incoming call.

When the ASP detects an incoming call it immediately starts storing the incoming audio. Within 5-10 msec the ASP sends a Zip tone to the switch to announce an incoming voice call.

The ASP stores up to 500 msec of incoming audio. After 500 msec of initial delay, it starts sending this stored voice to the switch from the very beginning, thus giving sufficient time for the receiving switch to connect the incoming voice call to the designated position.

When an operator answers the incoming call, the ASP starts looking for a pause in the incoming voice, and removes the initial delay. Therefore, the ASP incorporates 500 msec of delay ONLY during the initial call connect period. This process is totally transparent to the user. There is no delay for outgoing calls.

In case of an ASP failure a there is an automatic by-pass that permits normal communication without any loss of service.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


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