Re: HAW-1 (was: Colorado L-CXR data)
- --- In email@example.com, long-lines@a... wrote:
> What's a TASI?TASI = Time Assignment Speech Interpolation.
A room-sized (in the electron tube era) machine that doubled the voice
channel capacity of a submarine cable. It exploited the fact that any
2-way voice message circuit is generally idle in one direction (say
eastbound) while the other end is talking (say westbound).
TASI in the TAT-1/2, HAW-1 era took about 72 operator/machine trunks
and condensed them 2 to 1 to fill 36 physical channels in the cable.
The TASI at each transmitting end monitored each "derived" circuit for
talking or silence. When the circuit started talking, the TASI
assigned it to a cable channel. It sent commands over a data-link
channel that told the distant TASI to, for example, "Look at cable
channel 16 and connect the output to switching machine ("derived")
circuit number 56." The far end was simultaneously monitoring its
transmit side of all the derived circuits and sending similar commands
on the data link.
Private lines and Record Carrier (RCA/WUI/ITT) telegraph bearer
circuits were not connected through the TASIs. Adding a private line
took away one voice channel and had the effect of removing 2 "derived"
voice circuits from the TASI/cable.
This worked well in that era, since the traffic was all conversational
voice, not data - which requires a connection 100% of the time.
TASIs were installed on the SB (48 channel) and SD (140+/- channel
cables). By the time of the SF cables (early 70s), this channel
multiplication scheme was no longer necessary.