1. last updated March 8, 04M. Veeraraghavan1 TSI (Time Slot Interchange) Let the contents of time slots 1 through 24 be as shown on the incoming line. The switch configuration requires data in slot 1 to be read into slot 24 and vice versa, and data in slot 2 to be read into slot 23 and vice versa 1224 abc 12 cda d b 23 a b c d 1 2 24 writes in order of arrival permutes as per switch configuration and reads out

2. last updated March 8, 04M. Veeraraghavan2 From space switch to T-S-T switch The intermediate stage switch is a single switch of size: n12.... n12 n12 k12 k12 k12 k12 k12 k12 n12 n12 n12 TSI 1 TSI 2 TSI N/n TSI 2 TSI 1 The intermediate stage switch is reprogrammed for each of the k time slots. Replace each first-stage and every last-stage switch by a TSI. Replace multiple intermediate-stage switch with a single time-shared space switch.

3. last updated March 8, 04M. Veeraraghavan3 B VIEW WITH ANIMATION AC D Program the two sets of TSI stages and the intermediate space stage accordingly A->C, B->A, C->D, D->B The time to send three slots between 1 st stage and 2 nd stage is the same as the time to receive two slots into the 1 st stage. D1 could have been sent in the first slot on L2 because it could have been sent out on L4 in time slot 1 and then switched around by TSI 4 to the appropriate slot going to D 2 x 3 (TSI 1) B1A1 Connected to A and B B1A1 L1 2 x 3 (TSI 2) D1C1 Connected to C and D D1C1 L2 t=1 A1 L3 L4 3 x 2 (TSI 3) 3 x 2 (TSI 4) Connected to C and D Connected to A and B A1 B1 C1 B1 t=2 D1 t=3

4. last updated March 8, 04M. Veeraraghavan4 Programming the switch Means setting the operational behavior of all the TSIs and the time-shared space switch Previous slide example: –TSI1: TS1->TS1; TS2->TS2; blank->TS3 –TSI2: blank->TS1; TS1->TS2; TS2->TS3 –TSI3: TS1->unmapped; TS2->TS1; TS3->TS2 –TSI4: TS1>TS1; TS2->TS2; TS3->unmapped –time-shared switch at time = 1, cross-over at time=2, direct at time=3, cross-over