lELF.rilOML TK.I\SMISSI(}.\ M.IIMF.X.INCIL .17 



.1 >\vitrhl)t>.ir(l |i<>sitiiiii. Thr ntnis .iff piiki'd up .mil plii^j^cd dirrcllN- 

 into tlu' sfi as shown .mil mi-asinviiu'iits ni.uli' of ilu- lo>s of lioili the 

 i-onl .mil opir.itoi's liniiits. Trunk liniiit tisis arr ni.iilc .it ilic 

 switchl>oanls in llif s.inu- nianni-r as prr\ ioiisls- (k-sciilu'd foe loop 

 transmission li'sts on toll riri'iiits, portahU- inr.isurinj; siMs such as 

 shown in Kip. 7 jjcnorally hfinj; I'liiiilini-d for this work. Operators' 

 sets arc ins(HHti'd i)erio<licall\' and transmit Irr and riTi'i\tT crticienci^'' 

 tcstinv; im-thods are imder field trial wliieh pro\ ide a means for test- 

 ing these instruments in central otThces. The miscellaneous trans- 

 mission circuits in an office are testetl at the points where lhe\' can 

 Ik; most conveniently picked up. Tlie tests on toll test hoard circuits 

 are made at this board and in\-olve chiefly loop tests on the equip- 

 ment associated with the toll circuits in the office and tests on the toll 

 line circuits InHween the toll testboaril and toll switchboard. 



Transmission Tests on Machine Si.itchint; Circuits. The transmis- 

 sion circuits in panel machine switching systems are identical to those 

 in manual systems, while these circuits in stcp-by-step systems are 

 of a different design but essentially the same as far as transmission 

 losses are concerned. Transmission tests on machine switching cir- 

 cuits are similar to those on manual circuits but involve special methods 

 for picking up the circuits and holding them while the measurements 

 are made. The standard types of transmission measuring sets are 

 used in this work in conjunction with the regular testing equip- 

 ment provided in the machine switching offices and the methods 

 which have been developed offer a quick and con\enient means for 

 making the tests. In manual offices the circuits terminate in jacks 

 or plugs at switchboards where they are readily accessil)le. In ma- 

 chine switching s>stems, pro\ision is made for terminating the circuits 

 in jacks at test desks or frames where they can be picked iii) b\- 

 patching cords and tested as conveniently as the corresponding ty[)es 

 of circuits in manual offices. Machine switching systems otTer an 

 important advantage in transmission testing work, particularly in 

 trunk testing, in that the circuits to be tested can be looped auto- 

 matically b\' the use of dials or selector test sets, thereby doing away 

 with the necessity for ha\ing someone at the distant otfue i-nmplete 

 the loops manually. 



In panel machine switching offices the circuits involving trans- 

 mission equipment corresponding to cord circuits arc the "district" 

 and "incoming" selectors. These are tested by setting up the trans- 

 mission measuring set at the district or incoming frames and connect- 

 ing the set to the test jacks ass<jciated with the circuits. Tests on 

 trunks between manual and panel machine switching offices where 



