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I. The Talk-A-Phone Co. U. S. A. Service Center is located at 7530 North Natchez
Avenue, Niles, Illinois 60714-3804, telephone number (773) 539-1100, fax number
(773) 539-1241.
XI. Phone Line Specifications
A. MODE I Operation
The following criteria must be met by a phone line to insure proper functionality of the
FCC approved equipment. All voltages use Tip as ground when measuring.
1. On-Hook voltage must be less than or equal to –36 V (-50 V standard).
2. Off-Hook should be recognized in a maximum time of 300 ms.
3. At an Off-Hook voltage of –15 V, the current that is supplied must be no less than
20 mA and no more than 120 mA.
4. Dial tone must consist of 350 Hz and 450 Hz tones at –17 dB ± 0.5%.
5. The telephone line must generate Ring-Back consisting of 440 Hz and 480 Hz
tones at –17 dB ± 0.5%, with a duty cycle of 1.6 seconds on—4.8 seconds off ±
10% interrupted at 20 Hz.
6. The telephone line must generate a busy signal consisting of 480 Hz and 620 Hz
tones at –17 dB ± 0.5%, with a duty cycle of 500 ms on—500 ms off.
7. The telephone line must be able to recognize or send the following frequencies in
order to decode or transmit DTMF:
a) 685 Hz — 709 Hz
b) 757 Hz — 784 Hz
c) 837 Hz — 867 Hz
d) 925 Hz —957 Hz
e) 1189 Hz — 1229 Hz
f) 1314 Hz — 1358 Hz
g) 1453 Hz — 1501 Hz
h) 1607 Hz — 1659 Hz
8. When dialing, the telephone line should require a minimum tone pulse ON time of
40 ms, as well as a minimum between tone gap of 40 ms.
9. The telephone line should support and match with a 600W AC impedance, as
well as a DC resistance of 100 W — 200 W.
10. The telephone line should recognize a 450ms hang-up as a disconnect signal.
B. MODE II and MODE III Operation
Talk-A-Phone phones can be used with most PBX systems with non-standard dial
tones, ring-backs, busy signals and hang-ups.
Federal Communications Commission Information
Row 1
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Column 1 (1, 4, 7, *)
Column 2 (2, 5, 8, 0)
Column 3 (3, 6, 9, #)
Column 4 (A, B, C, D)
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