The interaction of telephony and video signaling places special demands on VDSL2 splitters. When a telephone is “off-hook,” the battery at the central office provides -48VDC over the phone line. When the phone is ringing, peak ring voltage is 127 volts. If the subscriber answers the phone (a condition called “ring trip”) at the negative peak of the voltage cycle, the instantaneous voltage (a combined -48VDC from the CO battery and -127 from the ringer) adds up to -175 volts. When this happens, an ordinary splitter can allow high-voltage, high-frequency transients to enter and interfere with the VDSL2 spectrum. This, in turn, can cause corruption or loss of data packets and interference with video signals.
The problem is not too significant in the case of data since TCP/IP can request packet retransmission. Video, on the other hand, is a streaming service and does not allow for retransmission. In order to provide uninterrupted video service and compete with video services on cable, the service provider must use high quality video-grade VDSL2 splitters. These splitters work with the DSL chipset to reduce or eliminate problematic ring trip effects. Appropriate splitters must be configured at the CO and in the network interface device at the customer premise.
See more VDSL2 considerations in our whitepaper.