900—9" H x 5-1/2" W x 3" D
The clock mounts on the side, and has a locked enclosure for the modem.

901—7-3/4" H x 7-3/4" W x 3" D
Open-back box to place over a wall outlet or to lock up power supply; slotted top for clock wires

900-DM—10-1/2" H x 9" W x 3" D
The 900-DM has a place for the duplex outlet to plug in the power supply, and can hold a modem and the 900 clock.

901D—7-3/4" H x 7-3/4" W x 3" D
Holds duplex outlet for power supply to clock and modem.