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CIRCUIT DESCRIPTION
P
6
AGE
Clearing
The 49018 can be cleared internally or externally. When
strapped for internal clearing, the digit counter is restored three
seconds after a complete code is received, whether it is valid or
not. When strapped for external clearing, the busy circuit and
the digit counter are restored by a “Power-up Clear”, a “Reset”
input, or by internal decoding a “*”, “#”, or “C” BCD input,
depending on strapping.
Internal Clearing: When the reset strap is IN, the interdigit
timer and reset circuit clears the entire station decoder three
seconds after the last digit is entered, or if three seconds pass
between digits. If the reset strap is OUT, the circuit wil not reset
after the last digit, but will reset if three seconds pass between
digits.
External Clearing: Three modes external clearing can be used
to clear or reset the 49018 subassembly:
♦
A reset (ground) is provided from the station or PABX/Trunk
Interface Module (44022 or 44023) at P2-8 or a “Power-up
Clear” at P2-9.
♦
The second mode is provided when the “#” or “*” BCD out-
puts of the supervisory decoder are strapped to the clear and
set outputs. Normally, the “#” is used to set the busy latch
and the “*” will clear the busy latch. This function can be set
to reverse the busy latch operation. The busy latch, when set,
provides a ground at P2-7 and applies a reset pulse through
the busy reset pulse circuit to clear the 49018 and prepare it
to accept the next address. The busy latch remains set until
it is cleared by the xternal reset, “Power-up Clear”, or an
internal BCD output from the supervisory decoder.
♦
The third mode can be used when the “A” and “C” BCD codes
are strapped IN and perform the same functions as described
for the “#” and “*” BCD supervisory decoder outputs.
Power-up Busy
A power-up busy input at P2-12 is provided to set the busy latch
when the power-up signal from the 44020 DTMF Decoder
Module is received. The busy latch may be cleared by external or
internal sources as described above.
Clear Output
A clear output (ground) is applied to the 44022 or 44023 inter-
face modules using P2-10 each time the 49018 is cleared.
Toll Restriction Outputs
A toll restriction output is provided whenever a “0” or “1” BCD
signal is decoded by the supervisory decoder. The “0” or “1”
outputs do not require a reset code. They are applied through
respective buffer drivers at P2-5 or P2-6 to an external device
when toll restriction to a public telephone is desired.
49018-0697 <90-00089>
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