Clock Device to Record Time of Appointments and Other Events
An ordinary clock, fitted with an electrical device to record the length of telephone conversations or appointment hours, or indicate when a door is opened, is shown in the illustration. The record is made by the hands in contact with brass rings attached to the face of the clock, the front of the rings being covered with white paper, dipped in a chemical, on which black dots are caused to appear, at each contact. By examining the dots and noting the items corresponding to them on a memorandum, the length of conversations, etc., may be observed.
The Electrical Device Attached to the Clock Records Contacts Made by the Opening of a Door, and the Using of a Telephone
Two rings of ¹⁄₁₆-in. brass, one within the other, and having side arms, are mounted on the front of the clock, as shown in the illustration. The ring on arm A should be slipped under both hands, and should have spring enough to hold it in contact with the small clock hand. The ring fixed to arm B must be in contact with the large hand, but must be some distance from the small hand and the smaller ring, so that they will not come into contact when the hands cross each other. An offset in the arm A, and a piece of mica insulation, are provided where the larger ring crosses the bar A. On the surface of each ring, between it and its respective hand, is glued a piece of white paper, cut to conform with the ring, but ¹⁄₁₆ in. larger, so as to extend over the outer edge of the brass rings. The rings of paper are saturated in a solution of potassium chloride and permitted to dry, before being placed on the brass rings.
A high-tension current, passing through the coil D, enters the arm A, passes to the small hand, to the large hand, and out at the terminal on arm B. Black dots will appear on the prepared paper at the position of the hands, when the contact is made.
The primary wires E and F may be attached to a doorbell or to a contact on the door, indicating on the prepared paper the length of time the door was held open, as well as the time at which it was opened. The arms A and B must be well insulated from one another. For greater accuracy in recording time, to within ¹⁄₂ minute, prepared paper dials, with hour and minute marks, coming into contact with the hands at small projections punched in the hands from their upper surfaces, should be used. An ordinary secondary coil from an automobile may be used, and if the clock has a wooden case, the arms may be fastened directly to it.