TEST ADAPTER. Continued
Diode CR1 prevents test adapter damage from accidental reversal of the power supply inputs.
Voltage regulators U1, U2, and U3 convert the input voltage to the voltages used by the UUT. The 1.5 V supply is
provided by a voltage divider composed of R12 and R13 tapped into the 6.75 V supply line.
All resistors used by the power supply, except for R3, are mounted on the test adapter power supply CCA
e. RF Signal Routing. This section routes RF signals to and from the reference radio and UUT antenna
connectors and the test equipment.
Relays K1, K2, and K3 control the flow of the RF signals. Each is controlled by the RF switch (S3). 27.5 V dc is
supplied to the positive control lead (+) of each relay. Each relays negative control lead (-) may be connected
to GND through the RF switch. When the negative control lead is grounded, current flows through the relay coil,
shifting the relay output from the NC output to the NO output.
Attenuators AT1 and AT2 decrease the signal strength of RF signals input from either the reference or UUT RTs.
This prevents damage to an RT from a high power input signal. AT3 provides a 50-ohm matching impedance to
the RF DET output.
f. Switching. The switching section is composed of a variety of switches which perform signal routing
functions. Table 3-1 describes them and their uses. The switches are shown in detail in the schematic of FO-19.
Table 3-1. Test Adapter Switches
Routes signals for testing to test equipment (to frequency
counter, DMM, scope channel 1, or handset).
Sets conditions on the AUDIO REF and AUDIO UUT connectors for
RF SWITCH (S3)
several audio and data operation modes:
UUT RT transmits digital data
UUT RT receives digital data
Either RT transmits or receives audio
UUT RT transmits analog data
UUT RT receives analog data
different RF paths for signals from either UUT or REF RT.
different combinations of voltage and GND to be sent to UUT.
paths for input of function generator or handset signals into UUT
Two-deck switch which selects signal from UUT or REF RT for testing
by the test equipment.