Operating instructions

OPERATING MANUAL 2945A
46882-311D 3-73
Return to the Rx TEST mode and check that the RF generator is active, then return to the
TONES, DCS mode. The DCS coded signal will be produced when the legend
Tone On is
displayed against
Tone Generate Mode:. See Tone ON/OFF control below.
Tone ON/OFF control
When the RF DCS ENCODER screen or the AF DCS ENCODER screen is displayed, the tone is
turned on or off by the orange [ON/OFF] function key.
If the DCS tone is ON and the Tx TEST, Rx TEST, Dx TEST or AF TEST mode selected, the
CTCSS tone will continue to be generated.
If the tones out routeing has been set to give RF tones, this is provided by modulation generator 2.
The legend
---DCS--- will be displayed against MOD2 FREQ on the RECEIVER TEST or DUPLEX
screens. If is selected, the DCS tones can be controlled by repeated presses of the orange
[ON/OFF] function key. If
is selected, the DCS tone is still controlled by the
[ON/OFF] key, but if a frequency is entered using the data keys or if the variable control is
adjusted, the DCS tone will cease. It can then be re-started only when the
RF DCS ENCODER
screen or the AF DCS ENCODER screen is displayed.
If the tones out routeing has been set to give AF tones, this is provided by audio generator 2. The
legend
--DCS-- will be displayed against AF2 FREQ on the TRANSMITTER TEST,
DUPLEX
or
AF TEST screens. If is selected, the DCS tones can be controlled by repeated presses of the
orange [ON/OFF] function key. If
is selected, the DCS tone is still controlled by the
[ON/OFF] key, but if a frequency is entered using the data keys or if the variable control is
adjusted, the DCS tone will cease. It can then be re-started only when the
RF DCS ENCODER
screen or the AF DCS ENCODER screen is displayed.
DCS transmitter encoder testing
The decoders within transceivers equipped with DCS signalling are usually programmed to
generate their code for inclusion on the reverse channel.
The DCS RF decoder function of this Service Monitor is able to demodulate the DCS signal and
display the digital data.
The DSC signal is fed into a comparator register and occurrences of bit patterns corresponding to
the three ‘fixed bits’ 0 0 1, of the coded signal are flagged.
23 bit samples of the coded signal are placed in registers with the occurrences of the 0 0 1
sequence occupying the 12, 11 and 10 bit positions. The value of the data in bit positions 1 to 9 is
decoded. This corresponds to the DCS code number.
The binary representations of all the decoded sequences are displayed, along with the DCS code.
The oct values are compared with the system permitted codes in a look-up table and the true code
indicated.
The user can select the decoder bit rate to match that of the system, within the range 100 bits/s to
200 bits/s. The modulation level of the data signal is shown on the display.
DTMF
Overview
Dual Tone, Multi-Frequency.
The DTMF tones function will generate and decode sequences, of up to 40 characters
corresponding to the standard DTMF frequencies.
The encoder allows the user to create characters sequences which are routed to the AF GEN
OUTPUT connector or to the RF generator modulators.
The decoder will accept up to 40 tone pairs, either from the modulation meter output or as AF
signals from the AF INPUT connector.