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Configuring T1 and E1 Port Parameters for CTP Bundles (CTP Menu)

This topic describes how to configure port parameters for T1/E1 interfaces.

Before you begin:

  • Disable the bundle before you modify the bundle options.

To configure port parameters for T1/E1 daughter cards for CTP bundles using the CTP Menu:

  1. From the CTP Main Menu, select 1) Bundle Operations.
  2. Select 1) CTP.
  3. Select a bundle from the list. The bundle port must have a T1/E1 daughter card installed.

    If you select an active bundle, you are prompted to disable the bundle before configuring it.

  4. Select 3) Port Config.
  5. Select 2) Interface.
  6. Select 1) Type and set the type to Optional Interface: T1/E1.
  7. Follow the onscreen instructions and configure the options as described in Table 1.

    The options vary depending on whether the bundle is T1 or E1 and whether fractional T1 or E1 is configured.

  8. To configure clocking for the port, select 3) Clock Config and configure the Clock Config option as described in Table 1.

BITS input is a T1/E1 line interface unit (LIU), with AMI (alternate mark inversion) encoding enabled and B8ZS/HDB3 (Zero Suppression) disabled. The equalization is set for a 0-133 feet cable. An internal 100 ohm termination is present, although it might need to be externally augmented based on the type of cabling used. Any valid AMI signal works properly and it is not restricted to only the "all 1" BITS signal but the ones density must be sufficient to prevent LOS (according to the ITU G.775 recommendation). The TTL input has a slice point of 3.3V/2 = 1.65V relative to chassis ground (GND). Therefore, any signal on the coaxial center conductor that transitions through that voltage registers a transition. There are many signals, besides TTL, that satisfy this criteria. An external termination must be provided that matches the impedance of the cable that goes to the BNC connector.

If you can configure the rate in CTP menu, then the TTL supports a frequency of 2048 KHz for the TTL clock input, provided the signal is good and noise-free (terminated properly). TTL is rate-agile, while BITS is restricted to T1/E1 frequencies.

The TTL input is high-impedance (no on-board termination provided) because a variety of cable types might exist that you can use to drive signal to this connector, such as RG-58 coax (50 ohm), RG-59 coax (75 ohm), or twisted pair (100-120 ohm). Instead of applying a particular impedance termination on the board and have it incorrectly done, we recommend that you configure the impedance termination based on your network environment. For example, a 50 ohm termination is needed if you are using RG-58/U coax cable, which has 50 ohm impedance.

Table 1: CTP Bundle T1/E1 Port Parameter Settings in the CTP Menu
Field Function Your Action

Port descriptor

Specifies a description for the port.

Enter a description of up to 64 alphanumeric characters. Do not use the following characters:

( ; ' " ) ]


Specifies the type of interface.

Select one:

  • T1

  • E1

  • Fractional T1

  • Fractional E1

Option (for T1)

Specifies the T1 encoding method used on this bundle.

Select one:

  • B8ZS

  • AMI

Option (for E1)

For E1 interfaces, configure the termination to work with either coaxial or RJ-48.

Select one:

  • RJ48

  • COAX

Clock synthesizer

The following clock synthesizer settings are set by the software, and you cannot change them:

  • For T1, the clock synthesizer is set to 1544 KHz.

  • For E1 the clock synthesizer is set to 2048 KHz.


Fractional channels

Specifies the number of fractional T1 or E1 channels to transport.

For T1, select a number from 1 through 24.

For E1, select a number from 1 through 31.

Fractional Frame Transport

For fractional T1, enables or disables fractional frame transport.

Select one:

  • y (yes)—Frame Transport—Framing bit is transported along with data, which results in data alignment with the frame.

  • n (no)t—Framing bit is not transported.

CAS support

Specifies the signaling method used for fractional E1.

Select one:

  • n (no)—Common channel signaling (CSS) is used. The common channel carries data messages that convey signaling for the circuits between two devices.

  • y (yes)—Channel associated signaling (CAS) is used. Each traffic channel has a dedicated signaling channel (channel 16).

Clock Config

Specifies the type of clocking for the port. The default value for Clock Config is CTP is Loop Timed.

Select one:

  • CTP is Clock Source—The PBX either returns the clock received from the CTP device, or it returns a clock that is traceable to the same source as the CTP node clock reference. You typically use this configuration when you configure the CTP device with a clock reference input.

  • CTP is Loop Timed—The PBX provides the clock, and the CTP device returns the same clock to the PBX. You typically use this configuration when the PBX has the more accurate clock source. You can configure the far end of the circuit with adaptive clocking to recover this clock if necessary.

  • CTP is Clock Source (Adaptive End)—The PBX returns the clock received from the CTP device, and the CTP device uses the adaptive recovered clock. You typically use this configuration when the CTP device does not have a reference input and the PBX typically requires a clock from the distant PBX.