The buyer is believed to be US cable giant Liberty Media, which already owns pan-European cable firm UPC as well as the six regional cable networks it bought from Deutsche Telekom last month.
NTL is facing investor panic as its share price continues on a downward trajectory. The Nasdaq-listed company reached a high of $109 (£73.83) in 1999, but is now valued at $4.60 (£3.12).
It is also seeking to sell its transmission business, which transmits the signals for ITV, Channel 4 and Channel 5 in the UK. It is expected to raise £1.2bn from the sale.
Cablecom has a 53% share of the Swiss cable market, with 1.4m subscribers.
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