For this purpose, they suspended the instrument to the end of a spring plate, fastened between the two contacts of the commutator. The circuit wire corresponds with this plate, and the two contacts correspond, the one with the telephone, the other with the bell. When the telephone hangs below the spring-support, that is, when it is not at work, its weight lowers the spring plate on the lower contact, and the communication of the line with the bell is established: when, on the other hand, the telephone is raised for use, the spring plate touches the higher contact, and communication is established between the line and telephone. In order to make the bell sound, it is only necessary to establish, on the wire which connects the line with the bell contact of the commutator, a breaker which can both join and break the current, and which communicates on one side with the contact of the bell, and on the other with its battery. The ordinary push of an electric bell will be sufficient, if it is supplied with a second contact, but MM. Pollard and Garnier wished to make this action also automatic, and consequently they devised the arrangement represented in fig. 53. [Illustration: FIG. 53.] In this system, as well as in those which have since been devised, two telephones are employed, one of which is constantly applied to the ear, and the other to the mouth, so as to make it possible to speak while listening. The telephones are supported by three wires, two of which contain flexible conductors, while the third only acts as a support. Two of the four wires of the two telephones are connected with each other, and the other two are connected with the two binding screws of the commutator _t_, _t′_: the wires without conductors are suspended to the extremities of the two flexible plates _l_, _l′_, which correspond with earth and line. When at rest, the weight of the telephones presses the two plates _l_, _l′_, on the lower contacts S, S′, but when the instruments are taken up these plates press against the higher contacts. The two bell wires terminate on the lower contacts, those of the telephones on the higher contacts, and one of the poles of the battery is connected with the lower contact on the left S′, the other with the higher contact on the right T. When at rest, the system is applied to the electric bell, and the current sent from the opposite station will follow the circuit L _l_ S S′ S′ _l′_ T, so that the call will be made. On taking up the two telephones, the circuit of the bell system is broken, and that of the telephones is established, so that the current follows the course L _l_ T _t t′_ T′ _l′_ T. If only one telephone is held at a time, the current is sent into the bell system of the opposite station, and follows the route + P S _l_ L T _l′_ T′ _t_ P --. In this way the three actions necessary for calling, corresponding, and enabling the corresponding instrument to give a call, are almost involuntarily made.