GSM T
ELEMETRY
S
YSTEM
2. SIM card
The unit will accept SIM cards of most types subject to the following restrictions.
1. Only 3 Volt SIM cards will be correctly read and older 5 Volt types will be ignored.
2. Some types of pay-as-you-go SIM cards may require regular call activity (once every six
months) to remain registered.
3. SIM cards that have been protected by means of a PIN (in a mobile phone) will not
operate in the unit.
4. Incoming voice calls to the SIM card should be barred before it is used in the GSM 250
unit to avoid any error messages being sent back to the user. This can be achieved by
calling the service provider.
5. The message memory of the SIM card should be clear before it is fitted to the 250 unit.
250
The SIM card should be inserted into the side of the module (marked Telit). The PCB may need to be removed
from the enclosure in order to insert the SIM card.
3. Input and output circuits
The two inputs are provided via screw terminals GND/IN1 and GND/IN2 terminals. These two volt-free
digital inputs are designed to be actuated by contact ‘switch’ closures across the input pins.
GND
IN2
GND
Users
Switch
contacts
DS250-5 Nov ’06
©2006
REG No 277 4001, ENGLAND.
IN1
Page 3
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