34
MDS P-60/P-60 HL Reference Manual
MDS 05-2818A01, Rev. C
Keyline Options
Several methods may be used to key the transceiver, depending on the facilities
available at the installation site and the design of the customer-supplied data
equipment. (See
Figure 18 on Page 35
.) This section discusses three common
keying methods. Contact the factory if additional assistance is required.
Positive or Negative Keying
One keyline option is to use a keyed 12 to 25 volt source or a fixed voltage
source and series relay. The relay contacts can be included in either the positive
or negative supply lead (see
Figure 18 on Page 35
, examples 1 and 2). The use
of an opto-isolator allows both keying supply leads to “float” above or below
ground. J1 Pin 7 must be positive with respect to J1 Pin 8. For keying supply
voltages higher than 25 volts, add a resistor in series with the connection to J1
Pin 7 (or Pin 8) to limit the keying current to 10 to 20 mA.
Internal Current Source Keying
Another keyline option is to use the on-board 12 volt DC supply. This is done
by adding a jumper from J1 Pin 7 to Pin 10. J1 Pins 8 and 11 are then connected
to the keyline relay contacts (see
Figure 18 on Page 35
, example 3).
Manual Keying Button (for test purposes)
A red pushbutton, SW1, is provided on the Interface/Utility Board to key the
transmitter manually when desired. This is useful during initial setup and
testing of the packaged system.
Additional Interface Connections
Two additional outputs are provided on J1 for custom applications: AC power
failure alarm, and the transceiver’s Received Signal Strength Indication
(RSSI).
AC FAIL—
Pin 9
H = AC Present—Approximately 11 Vdc through a 1 K
resistor
L = AC Failure—Ground through a 1 K
resistor
RSSI—
Pin 12
Same as transceiver’s RSSI output. Provides a DC voltage pro-
portional to the received signal strength. Range is approximately
zero to five volts DC through a 10K current limiting resistor.
Refer to the transceiver manual for additional RSSI information.
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