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6
Applications
The SX2120-SEQ can be used in four types of configuration: a single unit providing three
sequenced banks; an expanded system where the SEQ controls a remote turn-on SurgeX
providing four sequenced banks (or three banks with increased current capacity for one bank); a
ganged system where two or more SEQs are connected together such that they all turn on and off
at the same time providing three banks with increased current capacity for all three banks; a
cascaded system where two or more SEQs are connected together such that the banks turn on
sequentially from one SEQ to the next SEQ. Each configuration is covered separately in its own
section, but first there are some general points which apply to all types of installation.
6.1
General Points
Section 3.2 provides detailed information about the remote control connections. If you have not
already done so, please read section 3.2 before continuing. The information in section 6.1 applies
to all types of installations and you should also read this section before continuing further.
6.1.1
Controlling the SEQ
The SEQ is primarily designed to be used with momentary action switches. A momentary
switch is a switch where the contacts are closed only while the switch is actually pressed, such as
a push switch. Using momentary switches allows several switches to be connected in parallel so
that the SEQ can be controlled from multiple locations. A single push switch would cause the
unit to power-up on the first press and then power down on the second press. A dual momentary
switch, such as a center-biased rocker, or two separate push switches (one for UP and the other
for DOWN), can also be used with equal versatility. It is up to the installer to choose the
configuration. Whatever type of switch is used, switches with gold contacts are recommended
for the best long-term reliability.
Where there are multiple control locations it is advantageous to use the 12V dc output to drive
LEDs so that there is an LED at each control location. Up to four LEDs running at 10mA each
can be powered from the 12V dc output. Each control location then has an indication of the
operational status of the SEQ regardless of which location last initiated power-up or power-
down.
The SEQ also supports latching switches, contact closure and applied DC voltage, but these
types of input cannot be used with multiple control locations – they are intended primarily for a
very simple system or for hook-up to a central controller. The front-panel push-button will not
work with a latching switch, contact closure or applied voltage inputs.
6.1.2
12V DC Output
The 12V dc output can be used to drive LEDs thereby showing the operational status at remote
control locations. This output can drive up to 40mA which can power four LEDs at 10mA each,
or more LEDs at reduced current. A resistor is required for each LED to limit the current. The
