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FLEX-6000 Signature Series – FLEX-6000 Hardware Reference Manual

Page 26 of 48

7.4.7 Pin 9: +5VDC

This pin is a +5VDC output for use by external equipment. This pin is capable of sourcing

up to 500mA of current. A thermally resetting fuse will protect the radio from damage.

I - This pin is protected by a thermally protected fuse. If an over-current occurs, the fuse

will open and remain open until the overload is removed.

7.4.8 Pin 11: Accessory TX

This pin is a buffered PTT output identical to the three RCA connectors TX1, TX2 and TX3.

Refer to the SmartSDR documentation for information on how to configure this output.

7.4.9 Pin 12: SDA I/O

This pin is the data signal for an I2C serial communication channel. It is to be used with

external equipment. Refer to the SmartSDR documentation for more information.

7.4.10 Pin 13: Accessory TX REQ

This pin is an additional transmit interlock signal input. Refer to the SmartSDR

documentation for information on how to configure this input.

7.4.11 Pin 14: PTT in

This pin is a Push-To-Talk input. Ground Pin 14 to engage transmit.

7.4.12 Pin 15: SCL I/O

This pin is the clock signal for an I2C serial communication channel. It is to be used with

external equipment. Refer to the SmartSDR documentation for more information.

7.5 10MHZ REFERENCE CLOCK INPUT

The external reference clock input is used to synchronize the radio’s master oscillator.

Requires a 1.0v p-p minimum to 3.3v p-p maximum (4dBm min - +15dBm max), sine or

square wave signal.

7.5.1 Radio Oscillator Startup

The radio software samples the external clock input first, then the optional GPSDO (if

present), then the internal oscillator (FLEX-6500: TCXO, FLEX-6700/6700R: OCXO). Once an

active source is found, the radio software stops looking for any other clock source. If the

external source is lost, the radio will look for an active internal oscillator, but it will not look

for any other oscillator signal until the radio is powered off and re-started.

I - The external signal is only sampled at initial startup of the radio software. It is

necessary to make the external signal available on the rear panel connector before the

radio is powered up. Otherwise, the signal will not be used.

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