SAES-T-556 PDF - Circuit Quality and Performance - PDFYAR - Engineering Notes, Documents & Lectures

This article is about SAES-T-556 which is about Circuit Quality and Performance and download SAES-T-556 PDF for telecommunication and electrical engineers, supervisors and project managers, telecom QCs, telecom QC Supervisors. This is saudi aramco standards of Telecommunication Engineering based on international codes and standards and useful for telecom and electronics engineering knowledge to get job as engineers, QC Supervisors and QC managers, Engineering managers and technicians.

SAES-T-556 PDF Download

SAES-T-556

Download SAES-T-556 PDF

Circuit Quality and Performance

SAES-T-556 is a Saudi Aramco Engineering Standard (SAES) that establishes the parameters and standards for circuits used in data communication. It provides guidelines for the planning, commissioning, and maintenance of dedicated, switched, and supervisory channels in data communication circuits and networks.

The standard serves as a reference document for engineers involved in the planning of data communication circuits and networks, as well as for technicians responsible for the provision, commissioning, and maintenance of such circuits and networks.

In the context of SAES-T-556, dedicated circuits are specified for voice band communication. There are two types of circuits described:

Bell Standard C2-conditioned circuit: This type of circuit is suitable for higher-speed operations where a high standard of conditioning is required. It provides a well-conditioned environment for data transmission.
Unconditioned circuit: This circuit is primarily used for lower-speed operations. It does not have the same level of conditioning as the C2-conditioned circuit. However, with an appropriate modem, speeds of up to 4800 bit/s or higher can be achieved over an unconditioned circuit.

The choice of circuit type depends on the specific application and the modem being used.

The standard defines Test Level Points (TLPs), which are reference levels used for measurement purposes. TLPs are numerically equal to the level of a standard 1 mW test tone (0 dBm) applied at a point of zero relative level in the circuit.

In the data circuits described in this section, the zero relative level point is the transmit output of the modem. The TLP levels at other points in the circuit indicate the levels measured at those points when a 0 dBm test tone is applied to the circuit from the user’s location (modem transmit).

Measurements in data circuits are made at data level, which is 13 dB below the TLP (-13 dBmO). In voice band dedicated circuits, a point-to-point circuit is designed to have a nominal loss of 0 dBm end-to-end. Therefore, the transmit level at the modem is -13 dBm (-13 dBmO). At other points in the circuit, the measured levels will vary based on the TLP values.

For example:

At the MOD IN jack of a 4-wire carrier system (a -16 TLP), the measured level will be -29 dBm.
At the DEMOD OUT jack (a +7 TLP), the measured level will be -6 dBm (-13 dBmO).
At the far end modem receive (an O TLP), the measured level should be -13 dBm.

A tolerance of ±2 dB is allowed on the measured values. In multipoint circuits, the overall loss between the in-station modem and any outstation spur is designed to be 3 dB to compensate for branching points.

The C2-conditioned voice band circuits specified in SAES-T-556 are designed to use conventional telephone plant and equipment. These circuits can be presented as 4-wire circuits, either point-to-point or multipoint. The conditioning requirements for these circuits comply with Bell Standard C2. Here are the parameters and specifications associated with these circuits:

6.3.1 Loss:

For point-to-point circuits, the nominal insertion loss should be 0 dB ± 2 dB at 1004 Hz in the 4-wire mode.
For multipoint circuits, the nominal insertion loss should be 3 dB ± 2 dB at 1004 Hz in the 4-wire mode.
The short-term loss variation should not exceed ±3 dB.
The long-term loss variation should not exceed ±4 dB.

6.3.2 Attenuation/Frequency Distortion:

The loss at frequencies other than 1004 Hz should be relative to the loss at 1004 Hz and within the following ranges:
300 Hz to 500 Hz: -2 dB to +6 dB (positive indicates more loss)
500 Hz to 2.8 kHz: -1 dB to +3 dB
2.8 kHz to 3.0 kHz: -2 dB to +6 dB

6.3.3 Envelope Delay Distortion:

The variation in envelope delay distortion at frequencies other than the minimum delay should be as follows:
500 Hz to 600 Hz: 3.0 ms
600 Hz to 1 kHz: 1.5 ms
1.0 kHz to 2.6 kHz: 0.5 ms
2.6 kHz to 2.8 kHz: 3.0 ms

6.3.4 Frequency Error:

The frequency error between the two ends of the carrier section of the circuit should not exceed +5 Hz.

6.3.5 Single Tone Interference:

The single-tone interference should be at least 3 dB below the C-message noise limits.

6.3.6 Harmonic Distortion:

The relationship between the power of the fundamental and the power of the harmonics should meet the following requirements:
Fundamental to Second Harmonic: 25 dB minimum
Fundamental to Third Harmonic: 30 dB minimum

6.3.7 Phase Jitter:

The phase jitter should not exceed 10 degrees peak-to-peak in the worst case.

6.3.8 Phase Hits:

The number of occurrences of phase hits in excess of 10 degrees peak-to-peak should not exceed 15 over any 15-minute period.

6.3.9 Gain Hits:

The number of occurrences of gain hits in excess of 2 dB with reference to the received signal level should not exceed 15 over any 15-minute period.

6.3.10 Dropouts:

The number of interruptions or dropouts of duration exceeding 10 ms should not exceed 50 over any 24-hour period, with reference to the received signal level, at a threshold of 12 dB.

6.3.11 C-Message Noise:

The maximum level at the modem receiver should be 50 dBrncO.

6.3.12 C-Notched Noise:

The C-notched noise should be at least 24 dB below the received 1004 Hz test tone power.

6.3.13 Impulse Noise:

The number of impulse noise counts should not exceed 15 over any 15-minute period, at a threshold of 68 dBrncO.

Unconditioned Voice band Circuit

In addition to the requirements specified for C2-conditioned voice band circuits, the SAES-T-556 standard provides further specifications for these circuits. Here are the additional parameters and limits:

6.4.1 Loss: The nominal insertion loss of the circuit should be 0 dB ± 2 dB at 1004 Hz for point-to-point circuits and 3 dB ± 2 dB at 1004 Hz for multipoint circuits in the 4-wire mode. The short-term loss variation should not exceed ± 3 dB, and the long-term loss variation should not exceed ± 4 dB.

6.4.2 Attenuation/Frequency Distortion: Relative to the loss at 1004 Hz, the loss at other frequencies should fall within the following ranges:

300 Hz to 500 Hz: -3 dB to +12 dB (positive indicates more loss)
500 Hz to 2.5 kHz: -2 dB to +8 dB
2.5 kHz to 3.0 kHz: -3 dB to +12 dB

6.4.3 Envelope Delay Distortion: Relative to the minimum delay, the variation at other frequencies should be as follows:

Below 800 Hz: Not specified
800 Hz to 2.6 kHz: 1750 microseconds
Above 2.6 kHz: Not specified

6.4.4 Signal to Noise Ratio: The minimum signal to noise ratio for operation at 1200 bits/s is 14 dB if using FSK modulation.

6.4.5 The parameter limits specified in paragraphs 6.3.4 through 6.3.16 and paragraph 6.3.18 (from the previous section) are also applicable to this circuit type.

These specifications provide guidance for the design and performance requirements of C2-conditioned voice band circuits, ensuring the proper functioning and quality of data communication.

Switched Circuits

Switched circuits, as described in section 7 of the SAES-T-556 standard, refer to dial-up connections over the switched telephone network. Here are the parameters and their typical values for such circuits:

7.2 Loss: The insertion loss can vary between 4 dB and 12 dB at 1004 Hz, depending on the circuit length. The short-term and long-term variations should not exceed ± 4 dB.

7.3 Attenuation/Frequency Distortion: Relative to the loss at 1004 Hz, the loss at other frequencies should be as follows:

Below 300 Hz: 0 dB to in excess of +10 dB
300 Hz to 500 Hz: 0 dB to +8 dB (positive indicates more loss)
500 Hz to 2.8 kHz: -3 dB to +10 dB
Over 2.8 kHz: +3 dB to in excess of +10 dB

7.4 Frequency Error: The frequency error should be no greater than ± 5 Hz, although it may exceed this figure in some cases.

7.5 Envelope Delay Distortion: Relative to the minimum delay, the variation at other frequencies should be as follows:

500 to 600 Hz: 0.2 to 2 milliseconds
600 to 1000 Hz: 0.1 to 2 milliseconds
1000 to 2600 Hz: 0.5 to 2 milliseconds
2600 to 2800 Hz: 0.1 to 2 milliseconds

7.6 Single Tone Interference: Switched network conditions may introduce in-band signaling tones momentarily or through crosstalk at levels close to the signal level.

7.7 Harmonic Distortion: The power of the harmonics relative to the fundamental may reach up to -20 dB for the second and third harmonics.

7.8 Phase Jitter: The phase jitter may range from 0.2 to 5 degrees peak-to-peak, but it can frequently exceed 10 degrees on some connections.

7.9 Phase Hits: There may be 5 to 30 occurrences of phase hits over a 15-minute period, but busy hour conditions can lead to values exceeding 100 with a decision threshold of 10 degrees peak-to-peak.

7.10 Gain Hits: There may be 5 to 30 occurrences of gain hits over a 15-minute period, but busy hour conditions can lead to values exceeding 200 with a decision threshold of ±2 dB relative to the received signal level.

7.11 Dropouts: Due to potential faults or disconnections, there may be more than 50 interruptions exceeding 10 ms over a 24-hour period, using a threshold of -12 dB relative to the received signal level.

7.12 C-Message Noise: Depending on the circuit length and the number of switching points, C-message noise values can range between 15 dBrncO and 55 dBrncO. Busy hour conditions may affect this reading considerably.

7.13 C-Notched Noise: The level of noise should be at least 24 dB below the received 1004 Hz test tone power.

7.14 Impulse Noise: Switch operation and crosstalk within the exchange contribute to impulse noise. During busy hour conditions, the number of noise spikes can significantly increase. The number of hits typically ranges from 5 to 100 in 15 minutes at a threshold of 68 dBrncO.

7.15 Bit Error Rate: The bit error rate (BER) depends on the transmission speed. For rates commonly used over a single dial-up line (3200, 2400, and 1200 bit/s full duplex, and up to 480

0 bit/s half duplex), the BER can vary between 1 error in 10³ bits transmitted and 1 error in 105 bits transmitted. An accepted rate for dial-up circuits is 1 error in 104 bits transmitted.

7.16 Other parameters specified in Section 4, such as return loss, depend on telephony network maintenance practices and standards in the case of switched circuits.

These values represent typical measurements for dial-up connections and provide an understanding of the performance characteristics of switched circuits over the telephone network. Actual values may vary depending on factors such as circuit length, network conditions, and maintenance practices.

FAQs about SAES-T-556 PDF Download

Q1: What is SAES-T-556?

A: SAES-T-556 is a Saudi Aramco Engineering Standard that establishes parameters and standards for circuits used in data communication. It provides guidelines for planning, commissioning, and maintaining dedicated, switched, and supervisory channels in data communication circuits and networks.

Q2: Who does SAES-T-556 apply to?

A: SAES-T-556 applies to engineers involved in planning data communication circuits and networks, as well as technicians responsible for provisioning, commissioning, and maintaining such circuits and networks.

Q3: What is a Bell Standard C2-conditioned circuit?

A: A Bell Standard C2-conditioned circuit is a type of circuit suitable for higher-speed operations that require a high standard of conditioning. It provides a well-conditioned environment for data transmission.

Q4: What is an unconditioned circuit?

A: An unconditioned circuit is primarily used for lower-speed operations. It does not have the same level of conditioning as a C2-conditioned circuit. However, with an appropriate modem, speeds of up to 4800 bit/s or higher can be achieved over an unconditioned circuit.

Q5: What are some of the key considerations for data communication circuits and networks?

A: Some key considerations include circuit planning, provisioning appropriate conditioning for higher-speed operations, selecting the right type of circuit (e.g., C2-conditioned or unconditioned), and ensuring effective commissioning and maintenance practices.

Q6: Are there other relevant standards or guidelines related to data communication circuits?

A: Depending on specific requirements, there may be other relevant industry standards or guidelines that complement SAES-T-556. It is recommended to consult relevant industry resources for a comprehensive approach to data communication circuit planning and implementation.

SAES-T-556 PDF – Circuit Quality and Performance