Clear-Com HX System Frames - Manual (Page 49)

The general-purpose inputs operate in one of two modes: the opto-isolated
mode or the non-isolated mode.
The opto-isolated mode requires the externally connected equipment to
provide the current to power the general-purpose input. The non-isolated
mode does not require that the externally connected equipment powers the
general-purpose input. The current is supplied by a voltage output on the
GP IN connector.
To select a mode, move the J1 jumper on the CPU rear card to one of two
positions. The J1 jumper is located on the inner-matrix side of the DB-25
connector.
For opto-isolated mode, fit the J1 jumper across pins 1 and 2.
For non-isolated mode, fit the J1 jumper across pins 2 and 3.
It is recommended that the connector is set to the fully opto-isolated mode.
Opto-isolated mode
Figure 17: Opto-isolated mode
In this mode, a DC voltage of between 7 and 24 volts is required at the
EXTVIN+ pin with relation to the EXTVIN– pin. To cause an input to detect
an active signal, current must flow from the relevant input pin.
The external device should draw no current to cause an inactive input and
at least 5 mA to cause an active input. The opto-isolator drive line contains
a 1.5 kOhm resistor to limit the current through the opto-isolator. Therefore
the input pins can be connected directly to the EXTVIN– level to cause an
active input.
The voltage level at the external input pin should not be allowed to go below
EXTVIN– or above +6 V with respect to EXTVIN–.
49 Eclipse HX-Delta User Guide