We know that the Retevis RT3S, RT82, and the RT90's software is very similar. When we look at the radio software or on the radio menu, we can see there is a section called "Tx Mode".
Before we get to know the Tx Mode, we need to know what's the Channels Hang Time first.
We can set the different hang time. Within the setting time, press PTT the radio will transmit the last received channel. After know it, now let learn what's the Tx Mode.
It means when you press PTT, your radio will transmit the last received channel.
HandCH same with the channels hang time, it means within the setting time, press PTT will transmit the last received channel.
Last Call CH also means press PTT, your radio will transmit the last receive channel.
So we can know that there is no difference between "Last call CH" and "Last call Ch + HandCH".
Designed Ch means when you press PTT, your radio only transmit the Main Channel. No matter if there is a call before on another band channel.
Designed CH + HandCH, It means within the channels hang time setting, when you press the ptt, the radio will transmit on the last receive channel. without the setting time, when you press the PTT you radio will transmit on the main channel.
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