User Guide

TRM 900 Intergrator’s Guide
13
Electrical Considerations
Power Supply
The TRM 900 transceiver has a power supply connection on Pin 18 and Pins 23 to 28 of the interface
connector. Pins 1, 5, 7, 9, 30 and Pins 19 to 22 are connections to both power ground and serial interface
signal grounds. Note that these pins are tied to a common point on the TRM 900 transceiver. If there is
a potential for a ground path current loop due to improper power application, we recommend a fusible
link be inserted in the signal ground to protect the TRM 900 transceiver.
TRM 900 transceiver modems are designed to operate with unregulated DC voltage levels between 3.6
and 4VDC. The power supply must be capable of sourcing 2A.
Shielding Considerations
e TRM 900 transceiver is designed to operate in proximity to noise generating circuitry. However,
certain radiated or conducted frequencies may degrade the performance of the TRM 900 transceiver or
render it inoperable. When possible, provide well-grounded shielding between circuits that radiate, such as
power supplies, voltage-controlled oscillators, crystal oscillators and the TRM 900 transceiver.