D. McKinnon, ast technology Labs, Inc. (To be ansi/tia-571-B) Telecommunications Telephone Terminal Equipment Environmental Considerations

4.3.2.1.OPERATING VOLTAGES

4.3.2.2.INDUCTION FROM POWER LINES

The induced current at a telephone interface connecting to terminal equipment possessing a low longitudinal impedance usually does not exceed 100 mA rms (50 mA rms per conductor) when a low longitudinal impedance is present at the central office end.

Longitudinal voltages may be converted to metallic voltages because of system impedance imbalances, but the metallic voltages usually do not exceed 24.5 mV rms (60 dBrn with 3 kHz flat weighting).

4.3.2.3.POWER LINE FAULTS AND LINE CROSSES (LEVEL C)

Under power line fault conditions (which may induce high voltages into telephone lines) or with a power line cross (metallic contact between power conductors and telephone cables), protectors normally limit potentials appearing between the tip and ring conductors (or between tip/ring and ground) to less than 600 volts rms. In most cases, power-system fault detectors will limit the duration of such voltages to 5 seconds. However, high resistance faults can last indefinitely. Such fault conditions can cause a protector to permanently short either the tip or the ring terminal to ground, in which case the fault voltage may appear as a metallic voltage. Test methods for evaluating equipment under over-voltage conditions are given in UL-1950 and CSA C22.2 No. 950-95. Rationale for the test methods is given in Annex B.

4.3.3.LIGHTNING SURGES

4.3.3.1.GENERAL

All tests shall be conducted in accordance with the IEC 1000-4-5 (Ref. A16) and the specific requirements of this standard. The surge generator parameters, test set-up, and procedure for surging equipment given in IEC 1000-4-5 shall be used to the extent practicable.

Two surge generators are used for most tests, as shown in figures 2(a) and 2(b). One generator is used for telephone line surges and the other for the power line and ground path surges. The generator characteristics are detailed in IEC-1000-4-5³.

The level A and level B surges are representative of those occurring with properly grounded, operational protectors due to voltages induced into outside plant leads.

Abbreviations used in this section are as follows:

4.3.3.2. TEST MODES

The types of surges to apply are defined as follows:

1. 
   Type P surges are applied to branch circuit power connections of the terminal equipment with the equipment powered. Surges are applied between:
   

• 
  the phase conductor and neutral conductor,
  
• 
  the phase conductor and grounding conductor, and
  
• 
  the phase/neutral conductors and grounding conductor (common mode).
  

2. 
   Type M surges are applied to all outside plant tip-ring leads of the terminal equipment. For each pair of tip-ring connection points, surges are applied between Tip and Ring or, for equipment that has a grounding conductor, surges are applied between Tip and Ring with Ring grounded, and then applied between Tip and Ring with Tip grounded.
   
3. 
   Type L surges are applied to all outside plant tip-ring leads of terminal equipment that has a grounding conductor. For each pair of tip-ring connection points, surges are applied between tip-ring simultaneously and the grounding conductor.
   
4. 
   Type T surges are applied to branch circuit power connections and all outside plant tip-ring leads of the terminal equipment with the equipment powered. Surges are applied between the phase/neutral conductors and simplexed tip-ring leads. The grounding conductor (if one exists) is connected to simplexed tip-ring.
   
5. 
   Type G surges are applied to terminal equipment that have more than one connection to earth . Surges are applied between all combinations of:
   

• 
  power cord grounding conductors,
  
• 
  permanent connections to earth, and
  
• 
  functional grounds, such as the protector block ground and coaxial conductor sheaths.
  

6. 
   Type I surges are applied to all tip-ring leads of terminal equipment that has a grounding conductor and is subject only to intrabuilding surges. For each pair of tip-ring connection points, surges are applied between tip-ring simultaneously and the grounding conductor.
   

4.3.3.3.TEST PROCEDURES

The surges are applicable in all operating states of the equipment under test including connections to other equipment and grounding options. If the equipment uses a detachable line cord for its tip-ring connections, a test line cord having no more than one-half ohm per conductor shall be used to connect the equipment to the surge generator. Equipment states that affect compliance but cannot be achieved by normal means of power shall be achieved by artificial means. Any magnitude of voltage up to the peak level specified is applicable for equipment that has voltage limiting circuitry. Sufficient time shall be allowed between surges to prevent cumulative heating of components.

Surge parameters are given in the following table.

Type	Peak Voltage1) (volts)	Peak Current2) (amperes)	Application 3)	Between	Min. No. of Surges, each polarity
P-1 (level A)	2,500	1,250	Fig. 3 a)	L-to-N	8
P-2 (level A)	5,000	2,500	Fig. 3 b)	L-to-G, L/N-to-G	8
P-3 (level B)	5,000	2,500	Fig. 3 a)	L-to-N	4
M-1 (level A)	1,000	25	Fig. 3 c)		8
M-2 (level B)	800	100	Fig. 3 c) 10x560 s	T-to-R	4
M-3 (level C)	1,000	100	Fig. 3 c) 10x1000 s		1
L-1 (level A)	1,500	27.3/lead	Fig. 3 d)		8
L-2 (level B)	1,500	300/lead	Fig. 3 e)	T/R-to-G	4
L-3 (level C)	1,000	100/lead	Fig. 3 d) 10x1000 s		1
T-1 (level A)	2,500	500	Fig. 3 f)	L/N-to-T/R	8
T-2 (level B)	5,000	1,000	Fig. 3 f)		4
G-1 (level B)	5,000	2,500	Fig. 3 g)	G-to-G	1
I-1 (level A)	1,500	100	Fig. 3 d) 2x10 s	T/R-to-G	1

Table 4 – High Voltage Surges⁴

1. 
   Peak voltage is measured at the output terminals of the surge generator with the output terminated in at least 10,000 ohms.
   
2. 
   Peak current is measured at the output terminals of the surge generator with the output terminated in a short circuit.
   
3. 
   The waveshape (where specified) applies to both open circuit voltage and short circuit current, and gives the maximum rise time to peak and the minimum decay time to half-peak. . The current waveform decay to half peak should range between the minimum requirement and two times the minimum requirement for all load values from 0 ohms to 10,000.
   

4.3.4.ELECTROMAGNETIC INTERFERENCE

4.3.4.1.RADIO FREQUENCY (RF) IMMUNITY

Under normal operating conditions, most terminal equipment can be expected to encounter electro-magnetic field strengths of 3 V/m (rms) or less⁵ in the frequency range of 150 kHz to 150 MHz, and conducted RF signals on the telephone line and power line of 3 V (RMS) or less in the frequency range of 150 kHz to 30 MHz. The RF immunity test methods and performance criteria are contained in TIA-631 (Ref. A19).

4.3.4.2.EMISSION

Limits for radiated emissions, and conducted emissions on ac power leads, are specified in the FCC Part 15 Rules.

4.3.5.DISCHARGE

4.3.5.1.GENERAL

Electrostatic Discharge (ESD), either directly to equipment or indirectly to some nearby object, can be a significant cause of equipment failure or malfunction. In a network such as ISDN, the adverse effects of ESD on one piece of equipment can propagate to others connected to the network. Equipment can be susceptible to ESD effects at all stages of storage, installation, testing, operation, adjustment, maintenance, and repair.

An electrostatic charge may be developed on the human body, furnishings, and other objects as a result of everyday actions and activities. The simple act of walking on a carpet or other insulating flooring material can cause a charge to build up on an individual. The rolling or sliding of furnishings such as carts and chairs across the floor, as well as contact with synthetic fabrics used in clothing and furniture upholstery, can generate large electrostatic potentials.

While it may not be possible or practical to protect equipment from the maximum ESD that may be experienced, the intent of ESD testing is to stress equipment with typical electrostatic discharges.

All tests shall be conducted in accordance with the IEC 1000-4-2 (Ref. A20) and the specific requirements of this standard.

4.3.5.2.ESD SIMULATORS

1. 
   Type 1 (IEC model): The test network consists of a 150-pF capacitor discharging through a 330-ohm resistor⁶. This represents a human discharge through a small hand-held metallic object.
   
2. 
   Type 2 (Human Body Model, or HBM): The test network consists of a 100-pF capacitor discharging through a 1500-ohm resistor⁷. This represents a human discharge through a hand .
   

4.3.5.3.TESTING

4.3.5.3.1.Preparation

The test set-up for equipment is given in IEC 1000-4-2, Clause 7.1, “Test set-up for tests performed in laboratories.”

Prior to the application of the test discharges:

1. 
   The equipment under test (EUT) shall be configured with all necessary hardware and software and shall be operating in accordance to its design specifications. Networked equipment shall be connected in a normal network configuration.
   
2. 
   Equipment interface connection points, including power leads, that provide a path for electrostatic discharge currents during equipment operation shall be appropriately terminated⁸. For example, Tip and Ring shall be connected to a telephone network or a network simulator that provides loop current, ringing, and DTMF detection.
   
3. 
   The laboratory climatic conditions shall be 15-35°C, 30-60% relative humidity, and 68-106 kPa atmospheric pressure (3236 m above sea level to 383 m below sea level).
   
4. 
   The EUT shall be stabilized at laboratory conditions immediately before testing.
   

4.3.5.3.2.Test Modes

1. 
   ESD Simulator Application: Type 1 and Type 2 ESD simulators shall be applied to equipment in the manner and at the voltage levels given in the following table. If equipment is capable of having different installation means, such as with and without a grounding conductor, each possible installation means that can affect compliance shall be evaluated.
   
   
   

	Discharge voltage and method
Simulator	CONTACT (a)	AIR (b)
Type 1 (IEC model)	6 kV, direct and indirect	4 and 8 kV, direct
Type 2 (HBM) (c)	not applicable	15 kV, direct

Table 5 – ESD Discharge voltages and methods

Conditions applicable to table:

1. 
   Direct contact discharges are applied to conductive and static dissipative surfaces of the EUT that have a discharge path to the grounding conductor. Ordinary paint is not considered to be insulation and, therefore, painted metallic surfaces are subject to direct contact discharges.
   
2. 
   Indirect contact discharges are applied to both the horizontal and vertical coupling planes.
   
3. 
   Air discharges (sparking) are applied to insulating materials and to conductive and static dissipative surfaces that are floating (ungrounded). Coatings, including paint, that are designed to provide insulation are considered to render a metallic surface as insulated and, therefore, coated metallic surfaces are subject to air discharges.
   
4. 
   At the option of the manufacturer, a Type 1 (IEC model) simulator may be used.
   

2. 
   Number of Discharges: At least 10 positive discharges and 10 negative discharges shall be applied at each test point selected in accordance with 4.3.5.3.3.
   
3. 
   Frequency of Discharges: Any charge remaining on the EUT shall be bled off after each discharge via a high resistance to ground. Any effects on the equipment during the bleed-off are disregarded. The time between successive discharges shall be at least 1 second.
   

4.3.5.3.3.Determination of Test Points

Areas on the equipment that are likely to be touched during normal operation shall be scanned to determine their vulnerability to ESD. Examples of such areas include:

equipment enclosures and their seams sockets designed for metallic plugs such as telephone jacks exposed metallic shells of cable plugs and connectors test plug receptacles exposed structural frame areas

dials and keypads pushbuttons front panels circuit pack faceplates connecting cords light emitting diodes wrist strap jacks

switches displays lamps consoles handsets headsets speakers

Points that are found to be vulnerable to ESD during scanning shall be used as the test points. At least four test points shall be established for direct discharges, which are in addition to the indirect discharges to the vertical and horizontal coupling planes. Additional test points may be chosen.

Circuit packs (as stand-alone assemblies), backplanes, and other intentionally exposed wiring shall not be tested.

Scanning shall be performed by setting the ESD simulator to continuous running (typically at 20 discharges per second) while discharging to possible test points. Scanning should be conducted with an ESD simulator set at the specified test voltage. At the manufacturers option, when scanning insulated surfaces for breakdown, the scan voltage may be reduced from the specified test voltage in consideration of the altitude of the test facility⁹ by the following multipliers:

Altitude	Sea level	500 m	1,000 m	2,000 m
Multiplier	1	0.94	0.89	0.79

Table 6 – Test voltage vs. altitude multipliers

4.3.5.3.4.Test Procedure

In general, both direct and indirect discharges are applied for all operating states of the equipment. If discharges to an EUT while in a primary operating state (e.g., off-hook) are sufficient to evaluate the ESD vulnerability of the EUT while in a secondary operating state (e.g., hold), only the primary state need be tested. However, if the sufficiency of such a procedure is not known, then all operating states shall be tested.

A cordless telephone handset, while insulated from earth, is charged by applying direct contact discharges to exposed metal such as the antenna or charging contacts. The handset is then discharged to earth through the charging contacts by cradling the handset. This test method (known as a charged body test) is applicable to similar hand-held battery powered equipment.

The bottom of equipment not normally carried during operation, and installed only by service personnel, shall not be tested. If the equipment can be installed by users, the bottom shall be tested using the Type 1 simulator.

If a test point exhibits ESD sensitivity in more than one operating state, the ESD sensitivity for each operating state is to be evaluated by distributing the discharges over each operating state to be tested, e.g. 5 discharges on-hook and 5 discharges off-hook. However, no less than 3 discharges (of each polarity) shall be applied per operating state so the total number of discharges can exceed 10 of each polarity. For example, a test point could receive 3 discharges each in an on-hook idle state, on-hook ringing state, off-hook idle state, and an off-hook hold state, for a total of 12 discharges to the same test point.

Doors and panels are tested as follows:

• 
  if not required to be opened by the user, doors and panels shall remain closed during testing.
  
• 
  if required to be opened by the user (e.g., to access disc and tape drives), discharges shall be applied to wrist strap jacks located behind the door or panel. If there are no wrist strap jacks, parts behind the door or panel are treated as if the door or panel wasn’t present.
  
• 
  if required to be opened by service personnel during operation;
  

• 
  for doors and panels made of conductive materials and affixed to the equipment, direct contact discharges shall be applied to edges and inner surfaces of a door or panel while it is open.
  
• 
  for doors and panels either made of insulating materials, or not affixed to the equipment, indirect contact discharges shall be applied to a vertical coupling plane while the door or panel is open or removed from the equipment.
  

A test report, including the test points chosen, the test voltage, the operating states, the sequence of testing, and the test results, shall be prepared.

4.3.5.4.PERFORMANCE CRITERIA

4.3.5.4.1.Response Modes

The user’s perception of performance for equipment after a discharge, other than no equipment response at all, falls into one of the following categories:

1. 
   Non-recoverable: The user experiences a loss of expected service, such as equipment failure, loss of calls in progress¹⁰ (including incoming calls), data transmission errors that exceed one errored second, transmission drop-out that exceeds 1 second, and loss or corruption of stored information. For example, the equipment may be damaged (typically a semiconductor) or may experience a processor lock-up.
   
2. 
   Recoverable: The user perceives the equipment to have malfunctioned and must take some action that involves ordinary use to recover, e.g., pressing a DISPLAY button to reset a display. However, if a procedure such as power cycling is necessary to restore service, the error is considered non-recoverable.
   
3. 
   Temporary: The user perceives a temporary loss of performance (for example, an audible click, flicker on a video screen, data transmission errors that do not exceed one errored second or transmission drop-out that does not exceed 1 second), but normal service is not disrupted.
   

4.3.5.4.2.Requirements

The response of equipment to a static discharge is of a statistical nature. The equipment shall not exceed the following response mode distribution for each test point.

Non-Recoverable	Recoverable	Temporary
0%	10%	100%

Table 7 – ESD response mode distribution

The entries in the table apply to each test point, for each operating state, not the aggregate discharges applied to the entire equipment. For example, a 10% entry means that the indicated response is acceptable if it occurs on no more than 2 of the 20 discharges applied to each test point.

It is desirable for equipment to comply with the performance criteria when direct discharges are applied to internal areas that may be contacted during shipping, installation, maintenance, adjustment, or repair.

4.3.6.PERCEPTION CURRENTS

Perception current limits are specified to minimize discomfort to users and others who contact the equipment while it is in operation. The limits are based on the threshold of perception for sensitive persons.

4.3.6.1.New Title Required for this heading

For ac, dc, and combined ac and dc currents, the following limits apply (with any enclosure(s) in place) under all normal operating conditions (exclusive of surge voltages) and for all modes of operation of an equipment:

4. 
   (1) The current flowing through a 1500-ohm resistor to ground from any 100 cm2 (15.5 inch2) area, or the entire area whichever is smaller, of exposed surfaces (exclusive of grounded metal surfaces) shall be less than 0.3 mA peak.
   
5. 
   (2) The current flowing through a 10-kilohm resistor to ground from any 1 cm2 (0.155 inch2) area of exposed surface (exclusive of grounded metal surfaces) shall be less than 0.15 mA peak.
   
6. 
   (3) The current flowing through a 10-kilohm resistor connected between any two areas of ex-posed surface (exclusive of grounded metal surfaces) of 1 cm2 (0.155 inch2) each shall be less than 0.15 mA peak.
   

4.3.6.2.New Title Required for this heading

Perception current limits are frequency dependent. A frequency weighted equivalent peak as current I_e is employed for a sinusoidal current waveform of peak amplitude I, and is defined by:

for 0 < f < 10 kHz

for 10 kHz < f

for 0 < f < 10 kHz

for 10 kHz < f

where f is the frequency in hertz and I is the appropriate current limit from 4.3.6.1.

For ac waveforms composed of more than one frequency component, the equivalent current I_e is given by the sum of the equivalent currents of the sinusoidal components.

4.3.6.3.New Title Required for this heading

Transients less than 10 ms in duration should result in peak leakage currents less than

where I is the appropriate current limit from 4.3.6.1 and t is the duration of the transient (in ms).

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