Contributions to Physiol o<^cal Technique 



363 



case of fig. 3, the possible •uncertainty of the beginning and end of the 

 former approximating more or less to the time-interval of the clock.' 

 Signal 1 is therefore best used for such an event as an injection. If, how- 

 ever, the closure of the clock-contact be longer in duration than its opening, 

 as is the case vi^ith the Leipzig clock, the case is reversed, and Signal 1 be- 

 comes sharper than Signal 2. 



All three signals can be made by a single movement of the hand, by 

 means of a very simple switchboard consisting essentially of two spring 

 two-contact keys fixed parallel and close to one another on the same 

 board/so that one or the other or both together can be depressed at will. 



'Signal 1.' 



^'Signal 2. 



' ' Signal 



Fig. 3. —For description see text. 



One of them acts as a two-way switch, the other as a make and break 

 key. A complete scheme of connections is shown in fig. 4, A, and the 

 connections actually functioning in each case in fig. 4, B, C, D, and E. 

 Fig 4, B, shows the actual connections when time alone is being recorded. 

 Depressing the left-hand key (switch) produces Signal 1 by creating 

 the connections shown in fig. 4, C. Depressing the right-liand key 

 (key) produces Signal 2 by the connection shown in fig. 4, D^ De- 



1 The Brodie-Paliuer clock is usually made to drop eyery tenth second, as in the 

 tracings accompanying this paper. The lack of sharpness of Signal 1 may therefore rise with 

 it to two seconds, but this is of course not nece.s<ary when the time of occurrence of the 

 event to be signalled can be deliberately chosen. 



-' If Signal 2 be rapidly repeated by a succession of short taps on the right-hand key, 

 an additional easily di-stinguinlialile signal is produced more or less resembling on a 

 slowly moving drum the upper records of " teUmisations" in fig. 2, p. 362. This variation 

 can, of course, be also made use of with any ordinary signal not recording time with simply 

 a make and break key in its circuit. 



