You will probably need is a telephone card (Taxcard), which is available in post offices, stationery stores, or Swisscom shops. Some phone booths still accept coins, but they are not easy to find. If you’re planning to use a public phone, it is recommended to be get a telephone card.
Taxcards can be bought for CHF 5, 10, 20 or 50. Cards for CHF 20 or 50 have a band on each side of the card. When one band is exhausted, you must turn the card over and continue on the other side.
In most public telephone boxes it is also possible to be rung back. If so, you will find a sign with the phone’s number displayed on it.