ARTHUR H. BELL

In manufacturing establishments, schools, apartment houses and hotels, the intercommunicating telephone furnishes the most direct means of conversation between manager and workrooms, principals and subordinates, tenants and landlords.

In the installation of the equipment here described, particular attention is devoted to simplifying the telephone sets themselves, dispensing with induction coils and magneto signaling apparatus, and all strap keys and complicated hook contacts.

Fig. 8 illustrates one telephone set as used with this system. First there is a vibrating bell or buzzer of a type usually sold by dealers for door bell and general signalling. A pair of wires are connected with the bell binding posts. The terminals of these wires are to be connected later on to the main line wires.

One side of the bell is directly connected with an automatic hook which on upward contact, that is, when the receivhr is removed from the hook, puts the transmitter and the receiver in series circuit. The other side of the receiver takes a certain point of connection on the main line wiring. A series of push buttons is arranged, as shown in the sketch, for signalling purposes.

In considering the arrangement of line wires connecting the instruments together we will undertake a three party equipment as would be used between three floors of a factory or private office, work room and stock room of any establishment.

We will install the full length of the circuit, from the first telephone to the last, one pair of wires to be known as "battery" leads. These wires will terminate on a strip at each end. Also will be run three more wires over this same course. It will be advisable, if possible, to use different colored wires (annunciator) so that any one wire can be singled out for testing or connection of wires. This is not difficult to arrange, as annunciator wire comes in various colors, and the exact amount of wire of each color to be used may be estimated by the length of the battery leads previously installed.

It will be noticed in the diagram, Fig. 8, that one wire leading from the bell takes No. 5 wire, i. e„ the lower battery lead and the other wire of the bells takes the same number of conductor as is its station number. For example, bell wire for No. 1 station takes No. 1,; 2 takes No. 2 conductor, etc.

One side of a push button takes that number of conductor as is the number of the station it is to ring, and the other side or the push button, which is a common wire, takes the wire coming from the receiver, which takes the fourth wire in all cases.