| 摘要 |
<p>A copper wire pair linking network terminating equipment 3 in a home with a relatively localised multiplexer 2 eg. in a street cabinet carries high data rate eg. VDSL signals comprising eg. ATM and ISDN combined at the multiplexer. It is necessary for the multiplexer to be provided with a power supply but, in the event of failure of the power supply, VDSL signals could not be generated in the multiplexer. To provide some fall-back in such a case, a metal link from the local exchange to the network terminating equipment is formed eg. using relays A, B and C, permitting ISDN signals to be received in the home even though the higher data rate ATM has now failed. <IMAGE></p> |
