[Amps] ICOM "send control" timing

[jeff millar]

My Icom IC-746Pro has an output called the "Send Control Jack" and the 
manual says "Goes to ground while transmitting to control external
equipment such as a linear amplifier."  I didn't see any timing  
information.  Does anyone know the timing between this signal getting 
asserted and the output of RF?

Our VHF station uses a sequencer for normal operation, but I'm trying to 
prove we have safe operation in case the operator presses the Transmit 
butter on the front panel rather than keying the radio through the 
sequencer.

thanks,

jeff