Siemens TC35 - Manual (Page 30)

28
Startup
Activation of the PD_IN reset signal on
the power supply connection
The POWERDOWN line on the GSM
module is connected to the watchdog input
pin of the power supply ASIC, which can
only be switched off by changing the
watchdog condition. To do this, the PD_IN
Terminal reset line is active (high) for at least
3.5s. This results in immediate, "hard"
disconnection, with the TC35 Terminal
unable to sign off correctly from the base
station in the STANDBY and TALK operating
states .
In the case of this hardware shutdown, the
software is no longer able to respond before
the voltage is switched off. This corresponds
to a direct, unannounced disconnection of
the operating voltage. In the application you
can switch off or reset the module without
interrupting the input voltage supply.