VRC2000 Installation and Operations Manual Page 105
Technical or Setup Assistance
Telephone: 800.945.7730 (USA) or 801.975.7200 (worldwide) • Worldwide Web @ http://www.gentner.com
number in several locations. The user can also direct alarms occurring on
specific channels to report to a specific telephone number in the outbound
telephone number stack.
Unbalanced Audio Output
The VRC2000’s BNC connectors located on the unit’s rear panel provide
auxiliary audio connections. The connector labeled AUDIO IN is paralleled
with the telephone-receive audio. The BNC marked AUDIO OUT contains
the send audio. For electrical specifications, see Specifications (Page 90).
Status Channel Inputs
There are 16 status-channel inputs on the VRC2000. These inputs are
designed to accept either a TTL level or a dry contact closure. The status-
channel input is labeled STATUS on the VRC2000 rear panel. This
connector is a DB37M.
U39 and U40, 74HCT541 octal-line drivers, are used to output the status-
channel data onto the address/data bus. U39 monitors the condition of status
channels 1–8, and U40 is tied to status channels 9–16.
The operating input levels of the 74HCT541 are 0–0.8Vdc for logic 0 and 2–
5Vdc as logic 1. The absolute maximum input range of this chip is -0.2–
5.2Vdc. Since the VRC2000 reads status-channel inputs once every second, it
is recommended that a logic transition last at least one second to ensure
correct detection.
A section of the VRC2000’s memory map is dedicated to storing the
condition of each status-channel input. This table is recalled when status
channels are accessed via the appropriate DTMF tones.
Metering Channel Inputs
There are 16 metering-channel inputs on the VRC2000. Each metering
channel is programmable to measure -5–5Vdc or 0–10Vdc. Each metering-
channel input can also be internally jumpered to read -5–5mA or 0–10mA
for full scale. The input to the unit’s metering system is labeled METERING.
Each metering-channel input can measure linear, power-to-linear or calculate
indirect power. When measuring a linear potential, the result of the A/D
conversion is given. With power-to-linear conversion, a metering channel’s
input voltage will undergo a numeric conversion from that of an exponential
factor of a power meter to a linear presentation.
Indirect power conversion takes the two previous consecutive metering
channels and multiplies them together to produce a numeric presentation.
For instance, an indirect power conversion could be used to calculate the
power output of a piece of equipment by multiplying voltage by current.
U32 (an AD7506 multiplexer) is used as a switching network at the
metering-channel inputs. The AD7506 output contains the analog
representation of the input selected via the four address lines, A0–A3 or
metering channels 1–16. U37 (an AD573) is a successive approximation
analog-to-digital converter. Analog-to-digital conversion is done on a binary
weighted scale. Each of the 10 binary bits (1024) is compared with the input
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