1. A network adapter for a communications network having subscriber devices, a presence, location and availability system (PLAS), at least one home location register (HLR) and a short message service center (SMS-C), the network adapter comprising: a first interface interconnecting with the at least one HLR; a second interface interconnecting with the SMS-C; a third interface interconnecting with the PLAS; a first translator interconnected with said first interface to permit the network adapter to appear to the at least one HLR as the SMS-C; a second translator interconnected with said second interface to permit the network adapter to appear to the SMS-C as the at least one HLR, whereby the network adapter intercepts messages from the at least one HLR and forwards such messages to the SMS-C and whereby the network adapter intercepts messages from the SMS-C and forwards such messages to the at least one HLR; and a processor for extracting predetermined information about subscriber devices from such intercepted messages and transmitting the predetermined information to the PLAS through said third interface.