Besides being a data switch and multiplexer, a DSLAM is also a large number of modems, each modem on the aggregation card communicating with a subscriber's DSL modem.
A DSLAM is being a data switch. A DSLAM is being multiplexer. A DSLAM is also a large number of modems. Modems are each modem on the aggregation card. This aggregation card is communicating with a subscriber's DSL modem.