EA4TX RemoteBox Series Hardware Reference & Operational Manual page 26

Annex III – Inhibit and PTT signal - Yaesu
Yaesu radios (FT1000, FT1000MP, 20000, etc) use a DIN connector like this one:
The connection that needs to be made between the RemoteBox interface (DB9) and
the DIN connector is as follows:
Remember that you need to insert a 10K Ohm resistor between pins 1 and 8 of
the connector, as shown in this photo:
Page 26
Hardware Reference and Operational Manual: RemoteBox