The invention relates to a circuit arrangement for a telephone station with ground connection to a central supply device for the purpose of post-dialling signalling. The circuit arrangement operates independently of which terminal of an exchange battery in the central supply device is connected to ground. A second polarity reversal protection device (rectifier bridge) is used as an indicator of the polarity of the exchange battery, so that, dependent upon the polarity, different grounding paths are formed in the telephone station. The circuit arrangement is universally suitable for PBX exchanges.