Tait TM8250 Operator's Manual page 94

Transmit timer
Your radio may have a transmit timer that limits the amount
of time you can transmit continuously.
When the transmit timer is about to expire,
the message Transmit timeout imminent
appears in the display, the red LED flashes
and the radio gives three beeps.
If the transmit timer times out, the call clears down.
Call time limit
In MPT trunked mode, the length of your call may be limited
by the network or by your radio. Your radio may be
programmed to display the time remaining for your call.
When your call time is about to expire, the
message Call timeout appears in the
display, the red LED flashes and the radio
gives a repeated beep.
94 Operating in MPT trunked mode