IXTERTOLL TRUNK CONCKN'TltATl \(; EQUIPMKNT 313 



"Tens Groufi' ami "Tens f/a/r" h'clai/s for Incotnlntj Tninhs 



'Vho incoming trunk associated wilh ciicli controller are dixided into 

 inroups of ten. These groups are designated 0, 1, "J, etc. I'^ach tiunk in 

 the gi'oup has a unit designation 0, 1, 2, etc. wliich corresponds to the 

 \'ertical ot tlie switch to whicli it is coiniected. l''or instance, an incoming 

 trunk in group '2 which is connected to the lumiher 3 \ertical on the 

 switch is designated 23. Each group of liuid>:s has a common start lead, 

 (st), (See Fig. 2) to the controller which is grounded when any trunk 

 in the grt)up is calling for ser\-ice. Each ti-inik in the group of ten supplies 

 an indi\-idual lead us to the controlkM' which is also grounded when the 

 particular trunk is calling for ser\ice. 'This lead sei'\'es to identify the 

 units designation of the trunk. 



In the controller there is a group of tiu-ee relays associated with each 

 group of 10 incoming trunks (Fig. o). These are (1) the tens relay (tn-) 

 which responds to the ground on the st lead from the trunk group when 

 a trunk in that group is calling for service providing that the tens gate 

 is open as discussed below, (2) the units control relay (uc-) which 

 when operated connects the common group of units relays (uo-ug) to 

 the us leads of the grunk group, (3) the hold connect (hc-) which 

 when operated steers the hold magnet operating path to the hold mag- 

 nets associated with the trunks in the particular group. The uc- and hc- 

 relays do not operate until it is the turn of that associated trunk group 

 to be served. 



Two series chains, carried through transfer contacts on all of the tens 

 relays, control the operation of the units control and hold control 

 r(^lays. The operation of these relays and the manner of advancing selec- 

 tions from one group to another is best explained by the use of the 

 following example. Assume that incoming trunks in groups 1 and 3 have 

 originated calls resulting in the operation of the tni and tn3 relays. 

 Assume also that the controller is conditioned for the low to high direc- 

 rion of selection for incoming trunks. When the tni and tn3 relays 

 operate, they cause the release of the tens gate relays (TCii and tg2) 

 which close the gates to the operation of any other tn relays and operate 

 tiie ucl and hcI relays. When the units gates close as described later, 

 the tnI relay is released and the trunks in group 1 will be served. When 

 the last trunk in this group has been served the ucl and hcI relays 

 release and the uc3 and hc3 relays operate advancing the selections 

 into group 3. The tn3 and uc3 and iics relays then function in the same 

 manner as described for the Txi, I'ci and iici relays. If the direction of 

 selection had been from high to low instead of from low to high, group 

 3 would have been served first instead of group 1. 



