1. COMT 2201 Local Loop Functions COMT 220

2. 2 Telephone Network Architecture Customer Central Office, Class 5 Office Tandem Switch Local Loop Trunks “The Network”

3. COMT 2203 Local Loop Local Loop, 2-Wire Trunks 4-Wire Hybrid

4. COMT 2204 Local Loop Services (Provided by the Central Office) BORSCHT: –Battery –Overvoltage Protection –Ringing –Supervision –Coding –Hybrid –Testing

5. COMT 2205 Battery and Ringing Nominal voltage is 48 V DC Ringing uses 100 V AC Local Loop Ringer Switch Hook Dialer Hybrid Ear Mouth

6. COMT 2206 Supervision Loop Start –Switchhook, Local Loop, and CO Battery form a circuit. –Switchhook open = on-hook –Central Office cannot start a call, only send ring signal Ground Start –Start call by grounding either local loop wire –Can be started by either side

7. COMT 2207 Dialing 123 456 789 *0# Row Frequency Column Frequency