Fluke II Series Operator's Manual page 26

Rear Panel Connectors (cont.)
PHASE LOCK IN BNC Connector
Provides the input for an external signal onto
which the Calibrator can be phase locked (1V to
10V rms, 10 kΩ input impedance). The connector
shell is not connected directly to chassis ground; it
is connected internally to the OUTPUT LO binding
post. The maximum allowable potential between
the connector shell and chassis ground is 20V
peak.
IEEE-488 CONNECTOR
This is a standard interface connector for
operating the Calibrator in remote control as either
a Talker or a Listener of the IEEE-488 Bus.
RS 232C Connector
A male (DTE) serial port connector for transmitting
internal calibration constant data to a printer,
monitor, or host computer. This connector is also
used for remote control of the Calibrator.
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