T1 PRI For PBX Telephony
A T1 PRI, also called an ISDN PRI, is a "Primary Rate Interface"
providing 23 individual digitized telephone lines plus data such
as Caller ID on a single digital telephone trunk line. A PRI line
is usually much less expensive than a dozen or more analog business
Bonding T1 Lines for Higher
While a standard T1 line provides 1.5 Mbps upload and download
bandwidth, lines can be bonded to create total bandwidths of 3
Mbps, 4.5 Mbps, 6 Mbps, 7.5 Mbps, 9 Mbps, 10.5 Mbps and 12 Mbps.
An advantage T1 lines have over fiber optic connections is that
they are available nearly everywhere without special construction.
Channelized T1 vs ISDN PRI
T1 lines can support two protocols of switched circuit telephony.
Channelized T1 lines offer 24 phone lines using in-band signaling.
ISDN PRI, or Primary Rate Interface, offers 23 phone lines and
common channel signaling that can include data such as ANI Automatic
Number Identification or Caller ID.
Fractional T1 Service as a
Not all businesses need the full 1.5 Mbps of a T1 line, but want
higher availability and the dedicated bandwidth offered by T-carrier
digital service. In many cases, fractional T1 services offers
a fraction of the bandwidth at a lowered monthly lease price.
Fractional T3 service may also be available for bandwidth needs
between 1.5 and 45 Mbps.
T1 Line Bandwidth Explained
A T1 line is typically referred to as having a bandwidth of 1.5
Mbps. The precise line speed is 1.544 Mbps. However, the usable
bandwidth or payload is actually 1.536 Mbps. The difference is
8 Kbps which is used for line framing to keep the transmitting
and receiving ends of the circuit in synchronization.