COMMON CONTROL SWITCHING SYSTEMS 1089 



switch until :i grouiuled .station teriniiiul was found. The central office 

 equipment was then stopped but the station switch continued stepping 

 until the starting point for the next digit was reached. When the central 

 office equipment was ready for the next digit the process was repeated 

 until the called line Avas reached. 



The Lorimer system has now disai)pearetl from the scene in spite of a 

 number of attractive features. The reasons for this disappearance are not 

 clear from available records, but some reasonable conjectures can be 

 made. For one thing, the pre-set calling device must have been expensive 

 both in first cost and to maintain; it was also designed for a maximum 

 of four digits and a re-design for more than four digits w^ould have en- 

 tailed .substantial effort for developing both the calling device and the 

 central office equipment. There is also some evidence to indicate that 

 the system cost more than either step-by -step or panel. 



THE NETWORK AUTOMATIC SYSTEM 



The network automatic was a proposed form of semiautomatic in 

 which the subscribers retained their manual instruments and were served 

 by small unattended branch offices, each of which had a single group of 

 trunks to a central operator office. On originating calls the branch offices 

 acted as concentrators, automatically connecting calling lines to trunks 

 to the central office where the operators -were located and who asked for 

 the called number as in straight manual practice. Called Unes were 

 reached through the branch offices by the operators at the central office 

 who were pro\'ided with keysets to control the branch office equipment. 



SEMI-AUTOMATIC SYSTEMS 



There were several plans for other types of semi-automatic systems. 

 Most of them contemplated replacing the "B" operator by a machine 

 under control of the "A" operator. The plan of using machines under 

 (;ontrol of the "A" operators to replace the "B" operators w^as operated 

 successfully in Saginaw, Mich, with Strowger apparatus. A similar plan 

 was in operation in Los Angeles, and several groups of engineers studied 

 improvements and variations. 



STATUS IN 1905 



The status of automatic switching by 1905 w'as this: there w'ere several 

 single office cities which had commei'cial installations of Strowger stej)- 

 hy-stcp eciuipmcnt with severe limitations vvvw for this field of u.se; a 



