TELECOM Digest OnLine - Sorted: Re: Question About ROLM PBX Telephones

Re: Question About ROLM PBX Telephones

Fred Goldstein (
Fri, 10 Dec 2004 23:57:28 -0500

In V23 I590,

> ROLM was originally an IBM CBX / PBX voice switching venture that was
> in North America's arrival was purchased away from the German company
> SEIMENS. IBM made many advancements and improvements to the systems
> proprietary operating system and architecture (Americanizing it). IBM
> later sold the ROLM CBX / PBX product back to SEIMENS for a handsome
> profit.

That wasn't exactly how it happened. I was a BIG ROLM customer in the
late 1970s and early 1980s, beta tested their LCBX, and supervised a
bunch of them later. Interesting story, actually.

The company (the name was formed from the first letters of the four
founders' surnames, btw) was founded in Santa Clara 1969 or so. Its
first product line was a range of mil-spec computers based on Data
General's then-popular Nova 16-bit minicomputers. The FCC had just
authorized PBX competition in 1969, after decades of monopoly. A few
years later, ROLM needed a new PBX for itself and didn't like what was
on the market -- most systems in 1973 were either electromechanical
crossbars or wired-logic relays; the earliest electronic PBXs were not
very well made. So they designed their own, creating a new product

The first ROLM CBX came out in 1975. Within a few years, it went
through several major software releases, adding lots of features. The
early machines supported regular electromechanical keysets by means of
an electronic deskside adapter -- it was not terribly successful
though. In early 1979, with Release 5, they introduced a real
electronic phone, the ETS-100. It had nice feature buttons and
primitive Caller ID, showing the 4-digit calling extension number.
That was a *real* shocker to callers -- I had one of the first on my
desk at BBN, where I was in charge of the new LCBX. A few years
later, they introduced the Rolmphone series.

The original CBX suffered from a short-sighted design decision. In
1975, there were no cheap 64 kbps codec chips. So to save money, they
designed the system around a 144 kbps codec, which could have much
cheaper filters (12 kHz sampling instead of 8 kHz meant it could have
gentler rolloff). Line cards came in "interface groups" of three
boards: One line interface, one coder, and one decoder. A 3-cabinet
system could hold about 800 lines, depending on the mix of trunks. It
was huge by today's standards, but more compact than the
electromechanical switches that it replaced. Norther Telecom came out
with its SL-1 at about the same time, using standard 64 kbps coding.
Well, by 1978, 64 kbps codec chips were mass-produced and cheap, so
the SL-1 kept getting cheaper to build, unlike the CBX. By 1983 or
so, T1 trunk interfaces were becoming available, and ROLM's design
needed *six* boards and half a shelf to do one, recoding 64 kbps to
144 and back! And the new Rolmphones were 64 kbps too.

ROLM was in crisis, but kept it quiet. Along came IBM, who bought
into the company around 1984, buying it all a couple of years later.
They paid too much ... the whole design had to be redone. Not only the
144 kbps codecs, but the main software too was obsolete. The original
CBX code was very tight (bit-bummed) embedded code, hard to maintain.

The multi-node VLCBX, shipped around 1982 (about two years late), had
an improved code base, but was still no gem. IBM had its work cut out
for it. They updated the CBX into the 8750, and came out with a new
9750 with more backplane capacity. Redwood was the baby version. But
the "integrated voice/data" fad (VoIP is the same basic idea, albeit
in reverse) was over, and IBM discovered that they didn't need a PBX
in their product line. So they sold the whole thing to Siemens (at a
big loss), who eventually phased out the native ROLM products in favor
of designs based on their German HICOM systems. ISDN was a big deal
in Germany and HICOM was designed from the ground up for ISDN. It
wasn't a huge hit in the States and indeed Siemens/ROLM declined in
market share.

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