Compaq Armada 7400 Reference Manual page 169

The following information characterizes the requirements of the
host system in order to maintain the reliable use of the Compaq
Armada 7000 Series II (Series 577) modem:
The fax/voice modem requires a power supply voltage of
5VDC ± 5%, 12VDC ± 5%, or -12VDC ± 5%.
The host computer must provide a maximum of 950 mW
(U.K.) from the +5VDC power supply, and a maximum of
50 mW from the -12VDC power supply and the +12VDC
power supply.
The host apparatus must provide adequate power for the
modem and any other auxiliary apparatus drawing power from
it.
Failure to provide modem user's instructions with the host
computer will INVALIDATE modem approval.
The modem is approved only for installation in a host and with
host attachments that are either type approved for such
apparatus or, if supplied after 1st March 1989, are marked
with or supplied with a statement that the host is supplied
under General Approval Number NS/G/1234/J/100003.
Connections to and from the modem card are made via the
following port: DTE port (SELV) 80-pin edge connector on
modem PCB.
Ports for SELV circuitry should only be connected to like
SELV circuitry ports.
The modem is suitable for connection to the Public Switched
Telephone Network (PSTN) direct exchange lines and relevant
branch systems (PBXs).
A ringer equivalent number (REN) is a value given to all
apparatus to be connected to the PSTN. Its value can be taken
and used to calculate the maximum number of equipment