A buzzer or bell is made fast to the inside of the box, unless it is too large to fit conveniently, in which case it may be attached to the wall above or below the box.
Fig. 17 shows the wiring system for this outfit, which, when properly set up and connected, should operate on a circuit or line several miles in length, provided that the batteries are strong enough.
This system may be installed in the box shown in Fig. 13, the flexible cord containing two wires being attached to the binding-posts at the top of the box and to the posts at the end of the receiver. This system differs from the one shown in Fig. 6 only in the addition of receivers T and T 2, and in the substitution of the automatic lever-switches (L S and L S 2) for the plain switches (S and S 2) in Fig. 6. When the line is “quiet” the receiver (R) should be hanging on the lever-switch (L S), which rests on the contact-plate (A). At the opposite side of the line the receiver (R 2) hangs on the lever-switch (L S 2), which in turn rests on the contact-plate (A A). This puts the bell circuit in service.
PLAN OF TELEPHONE CIRCUIT, COMPRISING RECEIVERS, TRANSMITTER, ELECTRIC BUZZERS OR BELLS, LEVER-SWITCHES, PUSH-BUTTONS AND BATTERIES FOR STATIONS NOT OVER FIVE MILES APART.]
If the boy at the left wishes to call up the boy at the right he removes the receiver (R) from the hook (L S) and presses on the button (P B). This closes the circuit through the battery (C C C), and operates the electric buzzer or bell (E B 2) at the other end of the system, through line No. 1 and line No. 2. The operation may be clearly understood by following the lines in the drawing with a pointer. The boy at the left may keep on calling the boy at the right so long as the receiver (R 2) hangs on the lever (L S 2) and holds it down against the plate (A A). But directly the receiver (R 2) is removed, the lever (L S 2) flies up--being drawn upward by the spring (D) shown in Fig. 14--and closes the telephone circuit through the spring-contact (B B), at the same time cutting out the bell circuit. The boy at the left having already removed his receiver, the telephone circuit is then complete through lines Nos. 1 and 2 and batteries C C C and C 2 C 2 C 2, the boys at both ends speaking into the transmitters and hearing through the receivers. The contacts B and B B are made from spring-brass or copper, and are attached inside the boxes at the back, so that when the levers are up contact is made, but when down the circuit is broken or opened. In Fig. 18 an interior view of a box is shown, the door being thrown open and the receiver left hanging on the hook.