The Apple Duo Dock modem adapter card is a small expansion card for the Duo Dock and Duo Dock II docking stations, introduced alongside the PowerBook Duo series in 1992. It connects to the Duo Dock’s main logic board via a 10-pin header connector and routes the PowerBook Duo’s internal modem signals to an RJ-11 telephone socket on the rear panel of the dock. The card communicates with the modem installed in the docked PowerBook Duo through the dock’s 152-pin expansion connector and internal circuit traces, enabling modem use when the laptop is docked and its own rear RJ-11 port is inaccessible.
| Pin | Name | Description |
|---|---|---|
| 1 | LINET/R | Line/talk receive |
| 2 | DAA GND | Modem DAA ground |
| 3 | DAA GND | Modem DAA ground |
| 4 | DAA GND | Modem DAA ground |
| 5 | /RA DVR | Modem relay A driver |
| 6 | DAA ID IN | ID input |
| 7 | /RING3 DET | Ring detect signal |
| 8 | /RBDVR | Modem relay B driver |
| 9 | DAA CNTL | Modem DAA control |
| 10 | +5 V MODEM | +5 V power |
Notes
- When the PowerBook Duo is docked, its rear RJ-11 telephone socket is physically obstructed by the dock. The modem adapter card restores telephone connectivity by routing modem signals through the dock’s 152-pin expansion connector to an RJ-11 socket on the Duo Dock’s own rear panel.
- The 10-pin header mates with the side of the Duo Dock’s main logic board; all modem DAA (Data Access Arrangement) signals, relay drivers, and +5 V power pass across this connector.
- The DAA ground pins (pins 2, 3, and 4) provide separate analogue ground returns for the telephone line interface circuitry.
Signals
- LINET/R — Telephone line transmit/receive signal from the DAA
- DAA GND — Analogue ground for the Data Access Arrangement circuitry (pins 2, 3, and 4)
- /RA DVR — Active-low relay A driver; controls the telephone line relay
- DAA ID IN — Identification input from the DAA module
- /RING3 DET — Active-low ring detect signal from the telephone line
- /RBDVR — Active-low relay B driver; controls a secondary telephone line relay
- DAA CNTL — Control signal to the DAA; selects DAA operating mode
- +5 V MODEM — +5 V power supply to the modem adapter card