468 BELL SYSTEM TECHNICAL JOURNAL 



Signalling System 



In order to coordinate operations at the two terminal stations, an 

 order wire system is provided. There are four telephone sets at each 

 station; one on the attendant's desk in the ante-room, one concealed 

 inside the television booth, one in the control room, and one at the 

 control panels for the technical operator, who operates the small 

 switchboard which is part of the system. Two of the underground 

 cable circuits connect the two switchboards, so that there may be not 

 more than two separate conversations between stations at one time. 

 Ringing is accomplished by means of standard 20-cycle ringing current 

 furnished by the Telephone Company. 



During a demonstration, the attendants' telephones are connected 

 permanently over one of the cable circuits. To relieve the operators 

 of the duty of ringing each time the attendants wish to communicate, 

 a push button and buzzer are provided at each attendant's desk, 

 operated by the standard ringing currents simplexed on the synchro- 

 nizing circuit. This arrangement leaves the operators free to manip- 

 ulate the television apparatus. 



The two order wire circuits are each simplexed to provide two 

 additional circuits which operate signal lamps indicating to both 

 operators when either chair in the television booths is occupied and 

 turned in position. 



Discussion 



The primary objects in developing and installing the two-way 

 television system have been two. The first was to obtain information 

 on the value of the addition of sight to sound in person to per- 

 son communication over the telephone. The second was to learn 

 the nature of the apparatus and operating problems which are 

 involved in a complete television-telephone service. While the in- 

 stallation is entirely experimental, it is being maintained in practically 

 continuous operation for demonstration to employees and guests of the 

 Telephone Company, and interesting data are being gathered on all 

 aspects of the problem. 



It may be said without fear of contradiction that the pleasure and 

 satisfaction of a telephone conversation are enhanced by the ability 

 ot the participants to see each other. This is, of course, more evident 

 where there is a strong emotional factor, as in the case of close friends 

 or members of the same family, particularly if these hav^e not been seen 

 for some time. 



Were the television apparatus and required line facilities of extreme 

 simplicity and cheapness it would be safe to predict a demand for its 



