Troubleshooting
58 025-9567E
the DTMF pad show a single character representation, but the other keyboard keys show the
two character representations in Table 18.
Table 18. Keyboard Test Mode Responses
Key Display
SEND 1 (top send key) S1
SEND 2 S2
SEND 3 S3
SEND 4 (bottom send key) S4
ALERT AL
ENTER En
CLEAR ENTRY CE
Also whenever a key is depressed, one of the eight control relays should close. When a key is
released, one of eight tones should appear at the tone output. When a key is released, a four-
digit code will take the place of the key character in the display. The code can be used to
determine which control relay should be closed and what frequency should be present at the
tone output. Table 19 shows the displayed code verses the tone frequency and control relay
closed. The order of the table is the order in which the tones and relays will progress upon
each momentary key closure.
Table 19. Relationship of Display Codes, Tone Frequencies, and Control Relays
Code Tone Frequency (± 1%) Control Relay
0150 293.0 Hz 1
0100 439.0 Hz 2
0082 536.0 Hz 3
0068 646.0 Hz 4
0047 935.0 Hz 5
0033 1332.0 Hz 6
0022 1831.0 Hz 7
0010 2929.0 Hz 8
When a key is again depressed, the character code should display, the tone output should turn
off, and the next control relay should close. When it is again released, the display should
change to the next code and the next tone should be present at the output. When the test tones
are being generated, an oscilloscope on the tone output should show a waveform very close
to a sine wave. Each successive tone generated by the momentary key depression should be
of approximately the same amplitude (within 1 dB) unless pre-emphasis or de-emphasis is
used.
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