Cisco uses "PA" to describe their Port Adapter add-on interfaces. PA series
cards are used in 7000 series routers (and some configurations of access servers
(AS5800) and switches (Catalyst 6000)). Each PA module is 1.0" x 6.5" x 6.0",
although they come in a variety of configurations.
The Cisco Port Adapters have much more on-board processing capability than the
Network Module or Network Processor modules. These blades actually do a small
amount of pre-routing computation before handing packets to the Route Processor module
in the 7000 series routers. Because of this they tend to cost more than a
similarly-configured NM or NP card.
The PA naming scheme follows Cisco's "standard" abbreviations and once one
is familiar with several PA product codes, it is easy to decipher NM and
NP modules with similar functionality.
PA-4T: 4 synchronous serial ports
PA-A3-T3: 1 ATM DS3 port
PA-4E: 4 10BaseT Ethernet ports
PA-FE: 1 100BaseTX or 100Base-T4 Fast Ethernet port
PA-2CT1-PRI: 1 channelized T1 ISDN PRI port