ANSI SCTE 165-11:2019 pdf free download – IPCablecom 1.5 Part 11: Analog Trunking for PBX Specification
5.1 Functional Responsibility
To maintain compliance with the IPCablecom NCS specification [NCS], the Call Agent will remain responsible for all higher order functionality whenever possible. Only when timing is critical will the endpoint be responsible for the required functionality. For example, the endpoint is expected to out-pulse a string of successive digits when requested by the Call Agent. In this case, the endpoint is responsible for the timing of the duration of each digit and the delay between them. The endpoint is also responsible for all timing requirements related to the start method in use – wink, delay or immediate. In fact, the start method used by the interface is transparent to the Call Agent.
5.2.1 Loop-Start Line Interface
The NCS Line package defined in the IPCablecom NCS specification [NCS] is used to support loop-start lines. Loop-start lines are typically used for residential voice services, but MAY be used to support analog trunking for PBX.
5.2.2 Ground-Start Line Interface
Ground-start signaling interfaces are used to provide two-way service to customer-installation switching systems, e.g., legacy PBX systems. According to [ANSI 401] ground-start signaling for two-way dial facilities was introduced to reduce the likelihood of seizure of the line at both ends during the silent interval of the alerting signal. Ground-start signaling is typically used on one-way or two-way seizure PBX lines with Direct Outward Dialing (DOD) and attendant-handled incoming call service. Ground-start lines are also used for automatically originated data service. The two-wire ground-start line conductors transmit common-battery loop supervision, loop dial pulses or DTMF address signals, alerting signals, and voice-band signals.
5.2.3 DID PBX Trunk Interface
A one-way Direct Inward Dialing (DID) trunk interface as described in [TIA] is required to support a DID interface of a PBX. DID trunks can only make calls in the direction from the network towards the PBX. Electrically, a DID trunk looks similar to the reverse of a 2-wire loop-start interface. The PBX provides loop current by applying -48 volt battery to the ring lead and grounding the tip lead. The MTA signals off-hook and on-hook towards the PBX by closing and opening the loop. The PBX signals answer supervision (off-hook) by reversing battery and ground on the tip and ring leads [ANSI 405]. The PBX signals call release (on-hook) by restoring battery to ring and ground to tip. Since this is a one-way trunk, there is no ringing voltage as seen on a loop-start interface. The MTA may dial using either dial-pulse at 10 pulses per second with 300 ms between digits or DTMF at 10 tones per second. Dial-pulse may be done either by opening and closing the loop in a manner similar to loop-start dialing; or it may use battery and ground pulsing. With dial-pulse interfaces, the network typically only dials the last 2 or 3 address digits to minimize call setup delay.