User manual

3 Operation

3.1 Switching ON the modem

There are two ways to switch on the modem, once power is applied.

 assert TO_IN to high level for > 1s

 activate the RS232 control line DTR

The modem is fully operational after 4 seconds. Logging onto a network may take longer than

this and is outside the control of the modem. The modem can be configured to start up at the

time power is applied by permanently tying power connector signals TO_IN (pin 4) and VCC

(pin 1) together. In this case DTR must be used to switch the modem on again after it has

been switched off or reset, while power is still applied.

DTR must be cycled from low to high.

The TO_IN signal requires a positive “edge” (a sharp” signal transition from low

to high) to turn the modem on. This transition should be a rising signal from 0V

(GND) to VCC, or at least a large fraction of that voltage range, and must be

applied at the same time as VCC or after it. Very slow transitions (significantly

slower than many milliseconds) or very small transitions (e.g. only few volts

instead of 0V to VCC) will not turn on the module (since they are not considered

to be a “positive edge”).

Although this will not be an issue in almost all typical applications of the modem, please

consider following points:

 Large capacitors in your power supply which will lead to slow leading and falling edges (issue

does not apply with modern stabilized switching regulator power-adaptors) AND TO_IN tied in

parallel to VCC (instead of separate dedicated digital signal)

 Slow analogue signals used to assert TO_IN

 TO_IN signal not before VCC

All 3 cases above might prevent the modem from recognizing the power-up signal this is no

failure of the modem itself, the same would apply to almost any electronic device that provides

a separate “power-on” or “reset” signal.

If you are doubt, please

 Use the mains power adapter that is provided by your distributor and is know to work properly

with your modem

 Make sure that your signal and system design is according to the above

 Consult our support team that will be more than happy to assist you.