48 TM8000 Encryption Midian Encryption Programming and Service Manual
June 2006 © Tait Electronics Limited
4.2 Circuit operation
Audio buffering, gain reduction and amplification is provided by IC U7, a
quad Op Amp. This reduces the higher Tx audio level in the TM8000 radio
down to a similar level to the TOP radio, and then amplifies it back up again
after the encryption module, to match the TM level. This allows the same
module settings for TOP or TM8000.
Note TM8000 Rx levels similar to the TOP and the Op Amps in the
Rx path are mainly buffering the Rx audio signal.
The diagram that follows illustrates the operation of the XA2324-01
circuitry:
GPIO port
GPIO1 sends PTT to the module and GPIO2 detects PTT from the
module. As the module’s PTT line is common, D2 and IC U6 (a 4053)
isolate the two PTT lines and prevent the radio from locking up on Tx.
Encryption Module
TM8000
Options Board
Direct
Programming Cable
PTT
AUD_TAP_OUT
RSSI
Green
LED
F1
AUD_TAP_IN
TM8000 Main PCB
Programming
Computer
Microcontroller
Encrypt/Decrypt
Tx/Rx
Switch
Tx/Rx
Switch
KL3
Programmer
Rx/Tx data
RS 232
Code control bus
+5V
Ground
Mode
Tx-SC
Rx-SC
SC-Tx
SC-Rx
PTT
RXD
TXD
20 way edge connector
SK1
Radio Microcontroller
Tx/Rx
switch
Tx/Rx
switch
12
Channel/Code
display
Channel/Code
(up/down buttons)
SK1 External connector
Reset
SK102 Internal options connector
To Next Page
Loading...
Need help?
General
