RFC-1 Installation page 3.8
3.3.1 Analog Readings
Any telemetry channel can be a status channel on the RFC-1. Explained briefly, the RFC-1 has the capability to read
telemetry over a range of 0000 to 2040. If the reading is:
• Between 0003 and 2039 the telemetry is spoken as four digits
• Lower than 0003 the words "status off" are spoken
• Higher than 2037 the words "status on" are spoken
Thus, any channel can act as either an analog input or a status channel with no specific programming changes. A
voltage must be applied to a telemetry input indicate a change of status. The voltage will be interpreted as a logic
level signal by the RFC-1 using the rules listed above.
3.3.2 Status Readings
The diagram below shows how to wire a telemetry input for a status output. When the external contact is closed, the
channel will read "status on" and when the contacts are open the telemetry will read "status off".
Figure 3.8; Typical wiring for a normally open status channel
The power supply shown in the illustration can be a simple wall-plug transformer that supplies anywhere from 6 to 12
volts DC. A single power supply can be used for many status contacts. The external 1 KΩ resistor is added to
discharge the input smoothing capacitor on the RP-8 more quickly. Without this resistor it takes about 5 seconds to
reach a “status off” reading after the external contacts open. Adjust the telemetry calibration pot so that the system
reads "status on" when the external contact closes.
This example illustrates one method of generating a status indication. There are many others. For example, to read
a closed contact as "status off", connect the voltage source through a 1 KΩ resistor to the positive telemetry terminal
and bridge the contact across the positive and negative telemetry terminals. A closed contact will short the voltage
and produce a "status off" indication.
Figure 3.9; Typical wiring for a normally closed status channel
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