290 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1956 



manually initiated. This test is set up on the basis of the known concen- 

 trator passive line circuit capabilities. Should a line fail to pass this 

 test, the test circuit stops its progress and brings in an alarm to summon 

 central office maintenance personnel. The facilities of the line tester are 

 also used to establish, under manual control, calls to individual lines as 

 required to carry out routine tests. 



c. Simulator 



As the central office sends out scanner control pulses either no signal, 

 a line busy or service request pulse is returned to the central office in 

 each time slot. The simulator test equipment, shown in Fig. 30, was 

 designed to place pulses in a specific time slot to simulate a line under 

 test at the concentrator. 



In addition to transmitting the equivalent of concentrator output 

 pulses the simulator can receive the regular line selection pulses trans- 

 mitted to the concentrator for purposes of checking central office opera- 

 tions. It is possible by combined use of the line tester and simulator to 

 observe the operation of the concentrator and to determine the probable 

 cause when a fault occurs. 



d. Service Observing 



The removal of the line terminals from the central office poses a num- 

 ber of problems in conjunction with the administration of central office 

 equipment. One of these is service observing. 



To maintain a check on the quality of service being rendered by the 

 telephone system, service observing taps are made periodically on tele- 

 phone lines. This is normally done by placing special connector shoes 

 on line terminations in the central office. 



To place such shoes at the remote concentrator point would lead to 

 administrative difficulties and added expense. Therefore, a method was 

 devised to permit service observing equipment to be connected to con- 

 centrator trunks on calls from specific lines which were to be observed. 

 This mcithod consisted of manual switches on which were set the number 

 of the line to be observed in terms of vertical group and vertical file. 

 Whenever this line originated a call and the call could be placed over the 

 first preferred trunk, automatic connection was made to the service ob- 

 serving desk in the same manner as would occur for a line terminated 

 directly in the central office. 



In addition, facilities were provided for trying a new service observ- 

 ing technique where calls originating over a particular concentrator 



