Editing Cable telephony (section)

== Disadvantage ==

One possible disadvantage to digital cable telephone service is similar to a disadvantage of [[cable Internet access]], namely that the medium is shared, which could result in occasional delays and drops when high volumes of bandwidth are used or in some cases shared with entire neighborhoods.  These delays could be experienced during the "prime time" parts of the day, when heavy Internet usage and Internet streaming devices can make telephone calls on this system difficult.  However, by utilizing Cable Lab's Packet Cable interface specifications, cable operators are able to diminish the effects of heavy internet usage on call quality. This is done by way of QoS provisions present in the Packet Cable specifications.<ref name="test">[http://www.cablelabs.com/specifications/PKT-SP-DQOS-C01-071129.pdf], PacketCable™ Dynamic Quality-of-Service Specification.</ref>    

The second disadvantage it that this service requires power at the subscriber's end. In an emergency, if mains power is lost and without the [[battery backup]] unit provided at an additional cost by the cable provider, this telephone service ceases to function.  Traditional landline service from phone companies supply [[phantom power]] over the communication wires and therefore keep attached devices operational.