Table of Contents
Advertisement
C71 and R2 (Positive), R78, C72 and R71 (negative).
The analogue signal is converted into a digital signal in the BBIC IC6 pin 119 and 122. The
speakerphone switching and echo suppression functions are contained within the BBIC. The
digital data is converted again into an analogue signal in the BBIC's internal codec.
The analogue signal is fed from IC6 pin126, via T13 audio amplifier, T8 hookswitch (TP50), D8
bridge rectifier, to J1 tel. line connector (TP26 and TP40), and out to the telephone line.
6.4. Keyboard
The TCD715 is fitted with a keyboard which provides the user with comprehensive
speakerphone facilities, and includes a full numeric keypad for dialling out.The keyboard is
mounted on a separate pcb, and is connected to the main pcb via J3 connector.
Keyboard scan pulses and LED drive signals are fed from the BBIC address/data bus to the
keyboard via and connector J3.Key press information from the keyboard is fed via J3 to the
BBIC address/data bus.
6.5. RF MODULE
BLOCK DIAGRAM RF MODULE
6.5.1. RF MODULE (SEE BLOCK DIAGRAM Fig.22)
The RF Module consists of two main components: the PMB6610 transceiver and the PMB6818
power amp.
In the transceiver the 10.368MHz clock signal SYCL is multiplied to around 1.9GHz using PLL
(Phase Locked Loop) control.
The TXDA signal is used to control the modulation of this frequency to 1.87GHz to 1.93GHz.
Received signals are demodulated, filtered and sent to the BBIC via the RXDA line.
The RSSI (Radio Signal Strength Indicator) signal enables the implementation of diversity
switching whereby two antennae can be mounted in different orientations and their signals
compared. The one with better reception can be selected by the BBIC using the ANT1 and ANT2
26
Advertisement
Table of Contents
