# T3 Interface Options

Hold Time: Enter the number of milliseconds after an interface has transitioned from up to down (or down to up) before the interface is advertised to the system as being down (or up).

Clocking: Specifies the clock source.

Internal: Select this option to use the device's internal clock.

External: Select this option to use the DCE's clock.

Frame Checksum: Select 16-bits or 32-bits.

Transmitting Flag in Idle Cycles: Select 0x7E to be transmitted in idle cycles, or select 0xFF to be transmitted in idle cycles.

Start/End Flags on Transmission: Select Filler to send two idle cycles between start/end flags, or Share to share start/end flags on transmit.

C-bit Parity Mode: Select this option to enable C-bit parity mode, which controls the type of framing present on the transmitted T3 signal. When enabled, the C-bit positions are used for the FEBE, FEAC, terminal data link, path parity, and mode indicator bits. When disabled, the basic T3 framing mode is used.

Long Buildout: Select this option to use a cable length longer than 225 feet (68.6 cm) for copper-cable based T3 interfaces.

Respond to FEAC Loopback Requests: Select this option to have the interface respond to far-end alarm and control (FEAC) loop requests.

Payload scrambling: Select this option to enable HDLC payload scrambling on the interface. Both sides of the connection must either use or not use scrambling.

CSU Compatibility Mode: Sets the interface to be compatible with the channel service unit (CSU) at the remote end of the line. This allows the interface to connect with CSUs that use proprietary methods of multiplexing. You can also specify the Subrate value to limit the HDLC-encapsulated payload.

Diagnosis Options: Sets the Bit Error Rate Testing (BERT) parameters.

BERT Algorithm: Select an algorithm from the scrolling list.

BERT Error Rate: Enter a value between 0-7, which corresponds to a bit error rate from 10-0 (1 error per bit) to 10-7.

BERT Test Length: Enter a value between 1-240 seconds.

Loopback Mode: Specify None, Local, Remote, or (for T1 only) Payload.