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We’ll describe the possible values here, because they’re a good way to ex-
plain your UPS’s single most important interface property – the kind of
protocol it uses to talk with its computer.
apcsmart An APCSmart UPS and its computer also communicate
through an RS232C serial connection, but they actually use it as
a character channel (2400bps, 8 data bits, 1 stop bit, no parity)
and pass commands back and forth in a primitive language (see
APC smart protocol) resembling modem-control codes. The different
APC UPSes all use closely related firmware, so the language doesn’t
vary much (later versions add more commands). This class of UPS
is in decline, rapidly being replaced in APC’s product line by USB
UPSes.
usb A USB UPS speaks a universal well defined control language over a
USB wire. Most of APC’s lineup now uses this method as of late
2003, and it seems likely to completely take over in their low- and
middle range. Other manufacturers (Belkin, Tripp-Lite, etc.) are
moving the same way, though with a different control protocol for
each manufacturer. As long as USB hardware can be mass-produced
more cheaply than an Ethernet card, most UPSes are likely to go this
design route. Please note that even if you have a USB UPS, if you use
a serial cable with it (as can be supplied by APC), you will need to
configure your UPS as apcsmart rather than usb.
net This is the keyword to specify if you are using your UPS in Slave mode
(i.e. the machine is not directly connected to the UPS, but to another
machine which is), and it is connected to the Master via an ethernet
connection. You must have apcupsd’s Network Information Services
NIS turned on for this mode to work. It is a much simpler form of
running a Slave than the old Master/Slave code.
snmp SNMP UPSes communicate via an Ethernet NIC and firmware that
speaks Simple Network Management Protocol.
dumb A dumb or voltage-signaling UPS and its computer communicate
through the signal lines on an RS232C serial connection. Not much
can actually be conveyed this way other than an order to shut down.
Voltage-signaling UPSes are obsolete; you are unlikely to encounter
one other than as legacy hardware. If you have a choice, we recommend
you avoid simple signalling UPSes.
The table shown below lists the APC model supported, and the possible
kewords that you would use in the configuration with the listed cables. Some
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