Q. The PTL pin is described as "internally pulled to Vdd", yet the pin appears to be "active high". How do I use this pin in my circuit?

A. The PTL pin is internally pulled to Vdd, and it is also "active high". The PTL pin should be grounded in normal Rx mode operation to allow the CTCSS detection function to control the squelch path. Otherwise, the PTL pin will keep the squelch path open whenever the 165C/465 are in Rx mode.

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