latching coin control relay k3 having its relay coil divided into two half parts k3 responds to the 34 coin collect 34 signal by dropping coins present in a coin chute into a coin box and to the 34 coin return 34 signal by allowing the coins to drop into a coin return chute on the coin telephone so that the coins can be retrieved by the user of the telephone if one of the conductors 23 24 of the transmitter 14 are connected to ground due to a fault or a fraudulently applied ground connection such as a pin through the transmitter housing it follows that the 34 coin return 34 or 34 coin collect 34 signal applied to the tip lead will be leaked off via the fraudulent ground even if the ring conductor 1 is disconnected at the central office at that time and the coin collect relay will therefore be unable to operate end allow the coins stored in the coin chute to be dropped into the coin box a caller can after having made a toll call begin to make a subsequent local call and after receiving dial tone have the coins returned when he hangs up before dialling a number applicant 39 s invention prevents the fraudulent operation by means of a relay having coil k1 4 in the ring conductor 1 which is sensitive enough to operate four contacts k1c k1e k1b and k1d at the minimum current flow in the ring conductor which is fifteen milliamperes the leak path.