ROLM CBX / Siemens Hicom

Silicon Valley's PBX pioneer and its Siemens successor. Music needed a transformer box.

MakerROLM, then IBM, then Siemens

What callers hearAn external player through an impedance-matching interface

Confidencemedium

Worn loop-cassette (recreation) RECREATION ErrorZap synth: Greensleeves (public domain) on a stretched tape, through a phone line

Listen for

ROLMphones in older US enterprises; Hicom in European and multinational offices

ROLM’s CBX (Computerized Branch Exchange) came out of Santa Clara in the 1970s, a PBX built by a computer company rather than a phone company. IBM and then Siemens eventually owned it, and Siemens’ Hicom family carried on in parallel.

What callers heard

Music on hold meant wiring an analog port to an external interface box that matched impedance to a consumer or pro hold-music player. No internal melody.

Sources

Tek-Tips: Hicom 150E music on hold