system: You are a contract-analysis assistant performing a span-extraction task. You are given an excerpt from a commercial contract and the name of a clause type to locate within it.

Return the exact text of the requested clause, copied verbatim from the excerpt — identical wording and punctuation, with no paraphrasing, summarising, explanation, or added commentary.

The excerpt is one window of a much longer contract and often will not contain the requested clause. If the requested clause does not appear in this excerpt, respond with exactly: Not found.

Output only the extracted clause text, or the exact string `Not found.` — nothing else.

user: Contract excerpt:
"""
SIT sequences. The first type is used mainly in Europe. It consists of a sequence of three tones of identical durations. The second type is the one used in North America. There are several North American SIT sequences that are encoded using various combinations of frequency and duration for each of the three tones. The encoding has been standardized by Bellcore. Performance Requirements: 1. The UTD shall handle both types of sequences. 2. There is no talkdown performance requirement. The near end is always silent and does not interfere with far end SIT signals. Software License D2 Technologies, Inc. and Maintenance Agreement August 4, 1997 CONFIDENTIAL 37 3. There shall be fewer than 1 talkoff in 5 hours of voice when the detector is programmed with the recommended parameters. Assuming that each voice call is has an average of 2 seconds of voice, there shall be fewer than 1 talkoff in 9000 calls. A.5.3.1.9 Unknown Tone Any single tone, dual tone, amplitude modulated tone or single tone sequence that is not classified as a CP, SIT, CNG or modem ANS tone, shall be reported as an unknown tone. Performance Requirements: 1. Talkdown performance requirement [TBD] 2. There shall be fewer than 1 talkoff in 5 hours of voice when the detector is programmed with the recommended parameters (minimum tone duration 400 ms). Assuming that each voice call is has an average of 2 seconds of voice, there shall be fewer than 1 talkoff in 9000 calls. A.6 Multifrequency Tone Detection (MFD) The MFD algorithm module detects the presence of Rl, R2 Forward, and R2 Backward Multi frequency (MF) tones under a broad range of network conditions and under international telecommunications specifications. A.6.1 Functional requirements: Table A-10, Table A-11, and Table A-12 specify the nominal frequencies for the MF digits that must be detected. - ----------------------------------------------------------------------- F1 (Hz) F2 (Hz) 900 1100 1300 1500 1700 ------------------------------------------------------------- 700 1 2 4 7 Spare 900 -- 3 5 8 Spare 1100 -- -- 6 9 KP 1300 -- -- -- 0 Spare 1500 -- -- -- -- ST - ----------------------------------------------------------------------- Table A-10: Nominal MF R1 Frequencies and corresponding digit definitions Software License D2 Technologies, Inc. and Maintenance Agreement August 4, 1997 CONFIDENTIAL 38 - ----------------------------------------------------------------------- F1 (Hz) F2 (Hz) 1500 1620 1740 1860 1980 ------------------------------------------------------------- 1380 1 2 4 7 11 1500 -- 3 5 8 12 1620 -- -- 6 9 13 1740 -- -- -- 10 14 1860 -- -- -- -- 15 - ----------------------------------------------------------------------- Table A-11: Nominal MF R2 Forward Frequencies and corresponding combination numbers - ----------------------------------------------------------------------- F1 (Hz) F2 (Hz) 1020 900 780 660 540 ------------------------------------------------------------- 1140 1 2 4 7 11 1020 -- 3 5 8 12 900 -- -- 6 9 13 780 -- -- -- 10 14 660 -- -- -- -- 15 - ----------------------------------------------------------------------- Table A-12: Nominal MF R2 Backward Frequencies and corresponding combination numbers 1. Be configurable to detect either R1, R2 forward, or R2 backward MF digits on a per-call basis. 2. Detect the presence of all 15 R1, 15 R2 Forward, and 15 R2 Backward digits under a broad range of network conditions. 3. MF digit information is provided as soon as the minimum duration is met. This information is called leading edge detection. This allows the earliest possible response to the digit, such as in compelled signaling. 4. The trailing edge of a MF digit must be detected. This allows the system to delay any response (such as in compelled signaling) to the digit until it is removed. The criteria selected for trailing edge detection will debounce MF digits. 5. The DSP reports leading and trailing edge in the 8 ms block that they are detected. MF events are not buffered. Software License D2 Technologies, Inc. and Maintenance Agreement August 4, 1997 CONFIDENTIAL 39 A.6.2 R1 Detection Performance requirements: Table A- 13 consists of MF R1 tone detection performance requirements taken from CCITT/ITU Q310-Q331 and Bellcore TR-NWT-000506. Also shown is D2's MF R1 performance requirements, which is a superset of the CCITT and Bellcore requirements. - ------------------------------------------------------------------------------------------------------------------ Requirement - ------------------------------------------------------------------------------------------------------------------ Characteristic Bellcore CCITT/ITU D2 - ------------------------------------------------------------------------------------------------------------------ Frequency Deviation +/-(1.5% + 5 Hz) must +/-1.5% must accept Configurable choice of accept three sets of must accept frequency tolerance: +/-(1.5% + 5 Hz), +/-(1.5% + 10 Hz), +/-(1.5% + 15 Hz) - ------------------------------------------------------------------------------------------------------------------ Tone Duration KP signal >/= 54 ms >/=30 ms must accept Minimum duration is must accept; must reject steps, from 28 ms up. All others: >/=30 ms Can be configured
"""

Extract the exact clause related to "Volume Restriction" from the excerpt above.

assistant: Assuming that each voice call is has an average of 2 seconds of voice, there shall be fewer than 1 talkoff in 9000 calls.