Ascom chairman Juhani Anttila is to take on the dual mandate as CEO to steer the troubled technology group through a major restructuring.
The company announced on Friday that Urs Fischer would be stepping down as chief executive after less than two years in the job.
Ascom said that merging the two top jobs was necessary so that the pace of its restructuring "can continue to be guaranteed".
Fischer's departure is the latest in a string of resignations to hit the company, which has been trying to reposition itself as a telecoms provider - so far without much success.
It plunged into the red last year with a net loss of SFr396 million and again posted a first-half loss this year of SFr100 million on sales of SFr1.1 billion.
Over the past two years, it has shed around 1,250 jobs - 12 per cent of its workforce.
Ascom still has the support of its creditor banks, which have agreed to provide mid-term financing, but some of its products - most notably one which provides Internet access through power sockets - have failed to take off.
The company blames the global economic downturn for its problems, but the markets are clearly sceptical that the company can reinvent itself.
Its stock has fallen by more than 85 per cent this year, after slipping more than 70 per cent in 2001.
A report earlier this year on the firm's prospects by Geneva's Pictet bank warned investors to be wary of the stock.
"Ascom's track record makes it foolhardy to assume that this will be the final company facelift. We do not see any catalyst for Ascom's businesses that could set the company on a sustainable growth track," it added.
swissinfo with agencies
Ascom said merging the two top jobs was necessary to guarantee a speedy restructuring.
The firm is trying to reposition itself as a telecoms provider.
Fischer's departure is the latest in a string of resignations.
The company still has the backing of its banks, but investors have deserted the stock.