Issue 9, Amendment 1
September 2012
Contents
1.0 Introduction
1.1 Scope
The digital network interfaces covered in this specification include the following:
- Wide band channel which provides the full 1.544 Mbps ( DS-1 ) bandwidth facility or channelized into 24 subrate channels of 64 kbps interfaces;
- 1.544 Mbps ( DS-1 ) channelized into 24 subrate channels of 64 kbps interfaces using signalling bits which may be decoded by the network; and
- 1.544 Mbps ( DS-1 ) channelized into 24 subrate channels of 64 kbps having analog content which may be decoded by the network.
Note: Requirements in this part do not apply to ISDN interfaces. Refer to Part VI of this specification for all ISDN interfacerequirements.
1.2 Tables (Digital Interface Requirements)
Table 1 lists the generalrequirements to be met by all DS-1 digital interfaces.
Table 2 gives additionalrequirements to be met by DS-1 digital interfaces using signalling bits which may be decoded by the network.
Table 3 lists additionalrequirements to be met by DS-1 digital interfaces having analog content which may be decoded bythe network.
| Section | Requirements |
|---|---|
| 3.1 | General |
| 3.2 | Line Rate |
| 3.3 | Pulse Shape |
| 3.4 | Transmitted Digital Signal Power |
| Section | Requirements |
|---|---|
| 3.5 | Answer Supervision |
| Section | Requirements |
|---|---|
| 3.5 | Answer Supervision |
| 3.6.1 | Idle Sequence Signals |
| 3.6.2 | Metallic AC Energy |
| 3.6.3 | Encoded Analog Equivalent Transmitted Signal |
| 3.6.4 | Encoded Analog Equivalent Signalling Interference |
| 3.6.5 | Through Transmission Paths |
| 3.6.6 | Audio Signal Limiting |
| 3.6.7 | Automatic Dialling and Automatic Redialling |
1.3 Sequence of Equipment Testing
The tests shall be performed in the following sequence:
Compliance with each requirement in sections 3.5 and 3.6 shall be demonstrated at least once for any DS-1 subrate channel digital interface.
2.0 Preliminary Tests
2.1 Connecting Arrangements
Each digital interface on the terminal equipment ( TE ) designed for connection to 1.544 Mbps ( DS-1 ) digital interfaces shall be equipped with cable connectors in accordance with CS -03 Part III.
2.2 Preliminary Operational Check
Tests shall be conducted as described in the manufacturer's manual to verify that the TE digital interfaces intended for connection to 1.544 Mbps ( DS-1 ) facilities are fully operational.
3.0 Network Protection Requirements
3.1 General
Values ofresistors shown in document's figures represent the effective terminating impedance of theparticular circuit or interface.
When the TE makes provision for an external connection to ground, it shall be connected to ground. Whenthe TE makes no connection provision for an external ground, it shall be placedon a ground plane which is connected to ground and has overall dimensions atleast 50% greater than the footprint dimensions of the TE . The TE shall becentrally located on the ground plane without any additional connection to ground.
3.2 Line Rate – Pulse Repetition Rate
3.2.1 Requirements
The freerunning line rate of the digital signal shall be 1.544 Mbps with a tolerance of± 32 ppm (i.e. ± 50 bps ).
3.2.2 Method of Measurement
- Connect the TE to the test circuit shown in Figure 3.2.
- Verify that the output pulse options can be selected at the time of installation and select output (0 dB loss at 772 kHz ).
- Set the equipment under test to generate an all ones or dotting pattern.
- Adjust the spectrum analyzer centre frequency to 1.544 MHz , the resolution bandwidth to 10 Hz , or less and use a span of 200 Hz or less.
- Measure the resulting pulse repetition rate by recording the frequency of the peak entered on the display of the spectrum analyzer.
Notes:
- The spectrum analyzer should provide a high-impedance balanced input.
- Both the transmit pair and the receive pair should be terminated in the proper resistive loads.
3.3 Pulse Shape – OutputPulse Templates
3.3.1 Requirements
The shape of anisolated pulse, both positive and negative (inverted), shall have an amplitudebetween 2.4 and 3.6 volts, measured at the centre of the pulse, and shall fit anormalized template illustrated in Figure 3.3(a). The mask may bepositioned horizontally as needed to encompass the pulse and the amplitude ofthe normalized mask may be uniformly scaled by any factor needed to encompassthe pulse. The baseline of the mask shall coincide with the pulse baseline.
Note: The voltage, within a time slot containing a zero,may be greater than this limit because of undershootremaining from preceding pulses (i.e. inter-symbol interference). The use of alternate zeros and ones (dotting pattern) signal will minimize this problem.
3.3.2 Method of Measurement
- Connect the TE to the test circuit shown in Figure 3.3(b).
- Verify that the output pulse options can be selected at the time of installation, and set for 0 dB loss at 772 kHz .
- Set the equipment under test to generate a pattern which will allow the capture of an isolated pulse. This may be achieved by putting the equipment in loopback and using this DS-1 transmission set to send a suitable test pattern or by causing the equipment to send the test pattern using its internal generator.
- Record a single positive pulse on the oscilloscope and compare the pulse shape to the criteria. Refer to Figure 3.3(a).
- Record a single negative pulse on the oscilloscope and compare the pulse shape to the criteria. Refer to Figure 3.3(a).
| Nanoseconds (ns) | -500 | -250 | -175 | -175 | -75 | 0 | 175 | 225 | 375 | 750 |
|---|---|---|---|---|---|---|---|---|---|---|
| Normalized Amplitude | 0.05 | 0.05 | 0.8 | 1.15 | 1.15 | 1.05 | 1.05 | -0.07 | 0.05 | 0.05 |
| Nanoseconds (ns) | -500 | -150 | -150 | -100 | 0 | 100 | 150 | 150 | 300 | 425 | 600 | 750 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Normalized Amplitude | -0.05 | -0.05 | 0.5 | 0.95 | 0.95 | 0.9 | 0.5 | -0.45 | -0.45 | -0.2 | -0.05 | -0.05 |
Notes:
- The oscilloscope should provide a high-impedance balanced input.
- If the terminal equipment is capable of generating the test pattern internally and can operate using internal timing, the test may be performed without the data generator. In this case, terminate the receive pair with a 100 ohm resistor load.
3.4 Transmitted DigitalSignal Power
3.4.1 Requirements
3.4.1.1 Output Power
- The output power in a 3 kHz band entered on 772 kHz when an all ones signal sequence is being produced as measured across a 100 ohm terminating resistance shall not exceed +19 dBm .
- The power in a 3 kHz band entered on 1.544 MHz shall be at least 25 dB below that in a 3 kHz band entered on 772 kHz .
3.4.2.1 Method of Measurement
- Connect the TE to the test circuit shown in Figure 3.4 and select output pulse set to 0 dB loss at 772 kHz .
- Set the equipment to transmit an all ones data signal.
- Adjust the spectrum analyzer to obtain a 3 kHz pass band centred at 772 kHz .
- Measure the signal power at 772 kHz averaged over 3 seconds.
- Adjust the spectrum analyzer to obtain a 3 kHz pass band centred at 1.544 MHz .
- Measure the signal power at 1.544 MHz averaged over 3 seconds.
3.4.2.2 Alternative Method
- The following method of measurement may be used when an all ones condition cannot be achieved. The equipment should be configured to be transmitting idle channels with a stable bit pattern; that is, no signal input to the channel. Note the pulse density of the transmitted signal. This may be determined by examination of the pulse bit stream.
- Connect the TE to the test circuit of Figure 3.4 and measure the amplitude of a positive and negative pulse. These pulses should have both leading and trailing pulses.
- Calculate the power in
dBm
using the formula:
P772 ( dBm ) = 10 × log [(4/π × V × 0.707)2/200] + 30
or
P772 ( dBm ) = 6.08 + 20 × log (V)
where V is the arithmetic average of the absolute value of the pulse amplitudes found in step (2). - Measure the signal power at 1.544 MHz using the method described in Section 3.4.2.1 and calculate the all ones power by adding the appropriate correction factor for the ones density of the transmitted signal from Table 3.4.
| Ones Density (%) | Correction Factor ( dB ) |
|---|---|
| 12.5 | 18.1 |
| 25.0 | 12.0 |
| 37.5 | 8.5 |
| 50.0 | 6.0 |
| 62.5 | 4.1 |
| 75.0 | 2.5 |
| 87.5 | 1.1 |
| 100.0 | 0.0 |
Note: The spectrum analyzer should providethe correct termination for Tip and Ring leads via a high-impedancebalanced input across 100 ohms resistive load or via an appropriate BALUN.
3.5 Answer Supervision
3.5.1 Off-hookSignal Requirements for Access Channels that Correspond to Analog Loop-start or Ground-start Interfaces
Upon enteringthe normal off-hook state, in response to alerting, the TE shall continue totransmit the signalling bit sequence representing the off-hook state for 5 seconds unless the TE is returned to the on-hook state during the above 5-secondinterval.
3.5.1.1 Method of Measurement
- Connect the TE to the test circuit of Figure 3.5(a).
- Apply incoming alerting signal to the input of the TE .
- Set the TE to respond to the incoming signalling by whatever means are normal for the equipment (for example, by answering the call at the system console or by seizure of the associated analog channel).
- Immediately remove the alerting signal.
- Monitor the outgoing signalling bits from the digital equipment or the state of the associated companion TE for a minimum of 5 seconds to ensure that the TE continues to transmit the signalling bit sequence representing the off-hook state for 5 seconds, unlessthe TE is returned to the on-hook state during the 5-second interval.
3.5.2 OperatingRequirements for Access Channels that Correspond to DID Reverse Battery Trunk Interfaces
3.5.2.1 Reverse Battery Trunk Interface
For TE connected to reverse battery trunk interface, the off-hook state shall beapplied within 0.5 seconds of the time that:
- the TE permits the acceptance of further digits that may be used to route the incoming call to another destination.
- the
TE
transmits signals towards the calling party, except the call progress tones (e.g. busy, reorder and audible ring) and the call is:
- answered by the called party or another station;
- answered by the attendant;
- routed to a customer controlled or defined recorded announcement, except for "number invalid," "not in service" or "not assigned";
- routed to a dial prompt; or
- routed back to the PSTN or other destination and the call is answered. If the status of the answered call cannot be reliably determined by the TE through means such as detection of answer supervision or voice energy, removal of audible ring, etc., the off-hook state shall be applied after an interval of not more than 20 seconds from the time of such routing.
The off-hookstate shall be maintained for the duration of the call.
3.5.2.2 For Network Protection Devices
- Network protection devices shall block transmissions incoming from the network until an off-hook signal is received from the TE .
- Network protection devices shall provide an off-hook signal within 0.5 seconds following the receipt of an off-hook signal from the TE and shall maintain this off-hook signal for the duration of the call.
Note: The recommended solution is to select the timer value such that the duration of the one-way transmission path is short enough to not be noticeable to the calling and called parties.The recommended value is 4 to 8 seconds.
3.5.2.3 Method of Measurement
- Connect the TE to the test circuit of Figure 3.5(b).
- Activate A and B bits on the zero level decoder to simulate an incoming call on the reverse battery DSO channel under test.
- Using an oscilloscope, monitor the A and B bits transmitted by the TE and tip and ring leads of the called station.
- Observe and measure the elapsed period between the time that the called station goes off-hook to answer the call and the time that the outgoing A and B bits' status changes to answer supervision status.
- Ensure that the A and B bit status remains in the answer supervision mode for the duration of the call.
- Repeat steps (2) through (5) for each call answering mode as specified by the requirements (i.e. answered by the attendant, answered by a recorded message, forwarded call to another trunk, etc.).
