Specifications

TN438B central office trunk (8 ports)
Issue 6 February 2007 221
TN438B central office trunk (8 ports)
The TN438B CO trunk for Australia provides eight ports for loop-start CO trunks. Each of the
eight ports has tip and ring signal lead. The TN438B can detect 12-kHz and 50-Hz periodic
metering pulses from the CO. Additional features include call still held timing and automatic
guard fault-detection circuitry.
TN439 tie trunk (4 ports)
The TN439 tie trunk circuit pack for Australia and Japan provides four ports for 2-wire tie trunks
with loop disconnect signaling. The TN439 has administrable A- and Mu-Law companding and
administrable timers.
TN457 speech synthesizer
The TN457 speech synthesizer for British English provides four ports. These ports retrieve fixed
messages for leave word calling, automatic wake up, and attendant console features for the
visually impaired. These fixed messages include good morning, time-of-day, and extension
number. Each of the ports has touchtone detection. The TN457 speech synthesizer has
administrable A- and Mu-Law companding capabilities.
TN459B direct inward dialing trunk (8 ports)
The TN459B DID circuit pack for the United Kingdom provides eight ports for immediate- or
wink-start DID trunks. Each port has tip and ring signal leads. Each port is an interface between
a 2-wire analog line from a CO and the 4-wire TDM network in the system. The TN459B DID
circuit pack has administrable timers and a backward busy circuit that complies with signaling
requirements.