Telecommunications Industry Association TR41.1.1-06-02-006 Document Cover Sheet Project Number PN-3-0191 Document Title Research of Ringer Loads in other Standards Source AST Technology Labs, Inc. Contact Name: Don McKinnon Phone: 321-254-0268 Complete Address: 1430 Sarno Rd Fax: 321-254-9511 Melbourne, FL 32935 Email: dmckinnon@asttechlabs.com TR-41.1.1 Distribution Intended Purpose of Document (Select one) X X For Incorporation Into TIA Publication For Information Other (describe) – Incorporate into Document as an Informational Annex The document to which this cover statement is attached is submitted to a Formulating Group or sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of which provisions are hereby incorporated by reference. Abstract The following is the research result of ringer loads referenced in several Telcordia, TIA and ATIS documents. The purpose of this is to document a historical basis for the 5 REN 1386 ohms in series with a 40 uF capacitor load utilized in the PN-30191 draft document. Table Of Contents 1. Research Overview.......................................................................................................................... 2 Annex A Ringer Loads Used in other Standards ................................................................................... 3 A.1 Ringer Loads in Various Industry Documents ............................................................................. 3 A.2 Additional Information about Ringer Loads ................................................................................. 5 A.2.1 BRIEF: Reducing 5 REN requirement to 3 REN ..................................................................... 5 A.2.2 BRIEF: Rational for Ring Trip Immunity Network.................................................................... 5 v1.0 – 20050426 Telecommunications Industry Association 1. TR41.1.1-06-02-006 Research Overview A. For the Ringer Pre-Trip immunity test load, network documents for DLC and Central Office Equipment use 10K ohms, in parallel with a capacitance (2uf), in parallel with a 1400 ohm “Ringer Load”. B. For Ringer Pre-Trip immunity, PBX document TIA-464-C uses 15K ohms, in parallel with a 1400 ohm “Ringer Load”. C. The parallel 2uf capacitance for the network pre-trip immunity load is for a “very long and very leaky loop”. D. The 1400 ohm Ringer Load in the various documents are not all in agreement. Some have it defined as 1386 ohms in series with a 40 uF capacitor, others as five C4A ringers (110H at 3650 ohms + 0.45uF) and one even as a capacitance of 6 uF. Page 2 Telecommunications Industry Association Annex A A.1 TR41.1.1-06-02-006 Ringer Loads Used in other Standards Ringer Loads in Various Industry Documents Document GR-57CORE Issue 1, October 2001 (DLC) GR-57CORE Issue 2, 1993 5 REN Load Ring Pre-trip Load [5 REN Load = 1386 ohms + 40uF] [10 kohms // 2uF // 5 REN Load] 5.4.8 Ringing Capability A ringing load of 1 REN (Ringer Equivalent Number) has an impedance of 7000 ohms at 20 Hz. Thus, a load of 5 REN has an impedance of 1400 ohms at 20 Hz. A 1386 ohm resistor in series with a 40 μF capacitor should be used as a 5 REN load for the above criteria. 5.4.5 Ring Trip Immunity R5-136 [539] A RT line unit shall not trip ringing when it applies an alerting signal to a termination of 5 REN in parallel with 10 kohms in parallel with 2 μF applied tip-toring directly at the output of the RT unit. A termination of 5 REN is defined as 1386 ohms in series with a 40 μF capacitor… 5.4.8 Ringing Capability Same as above 5.4.5 Ring Trip Immunity [10 kohms // 8uF] Note: See item A.2.2 (last page) for additional information on this load. (TR-NWT000057) GR-506CORE ISSUE 1, JUNE 1996 [5 REN Load = 1386 ohms + 40uF] [10 kohms // 2uF // five C4A ringers] 14.1.1 Ringing Source Criteria R14-6 [544]An SPCS shall provide a minimum ringing voltage of 40 V rms across a ringing load of 5 REN at the end of any access line with a loop resistance ≤ (Rdc – 400) ohms. Part 68 of the FCC Rules and Regulations require that all registered customer installation equipment that can affect on-hook impedance have a Ringer Equivalence Number (REN). A ringing load of 1 REN for equipment designed for 20 Hz ringing has an impedance of 7000 ohms at 20 Hz. Thus, a load of 5 REN has an impedance of 1400 ohms at 20 Hz. A 1386 ohm resistor in series with a 40 μF capacitor should be used as a 5 REN load for the above criteria. 14.1.1 Ringing Source Criteria R14-23 [561]The alerting signal shall not be removed when applied to a zero-ohm loop with the following components connected in parallel from the ring conductor to the tip conductor of the interface. …— 2 microfarad capacitor; …— 5 C4A ringers; …— 10,000 ohm resistor. Page 3 Notes: 1. The C4A ringers are not defined in this document and no reference was provided. 2. See T1.401 section for the C4A definition. Telecommunications Industry Association Document TR41.1.1-06-02-006 5 REN Load Ring Pre-trip Load [5 REN Per TR-NWT-000057] [10 kohms // 6uF] GR-909CORE 4.5.9 Ring Trip Immunity R4-156 [202] Ringing shall not be tripped when an alerting signal is applied to a termination consisting of 10 kohms in parallel with 6 μF applied tip to ring directly at the output of the ONU. Issue 1 March 2000 (FITL) R4-157 [203] Ringing shall not be tripped when a 200 Ω resistance is applied for 12 ms or less directly at the output of the ONU. [Not Defined] [15 kohms // 1400 ohms (not defined)] Note: Section 5.4.3.1.1 PBX ringing states 5.4.5 Ringing Pre-trip shall comply with Table 10. To assure adequate protection against false Table 10 - PBX Ringing Voltage Ranges ringing trip, the PBX ringing trip circuit shall not trip ringing when tested under the and Terminating Impedances following conditions: Ringing Terminating Ringing Frequency Impedance Voltage (Hz) (V rms) (Ω) TIA-464-C, 2002 17 – 23 10,000/(N) 55 - 130 20 8,000/(N) 40 - 130 27 – 33 10,000/(N) 95 - 130 Where (N) = the number of station ringer equivalence with which the PBX is designed to work. (1) A terminating impedance simulating on-hook impedance, connected across the station line conductors and composed of the parallel combination of 15 kΩ resistance and a series connection of resistance and capacitance whose impedance at the specified frequency is as shown in Table 11. (=1400 ohms) Note: Section 5.4.6.1 Recognition of Idle Condition 5.4.6.1.1 The PBX shall recognize a resistance of greater than 15 kΩ tipto-ring at the station interface as an on-hook signal. [Not Defined] [Not Defined] Notes: T1.4012001 1. Does state use of C4A ringer load for NI Pulse Dialing criteria. C4A = 110H at 3650 ohms + 0.45uF 2. GR57 also states the same text as T1.401-2001 for pulse acceptance Page 4 Telecommunications Industry Association A.2 TR41.1.1-06-02-006 Additional Information about Ringer Loads Additional information was found in a Telcordia Report of Issues, GR-57 ILR. A.2.1 BRIEF: Reducing 5 REN requirement to 3 REN PROPOSAL(S): The 5 REN load was set by the FCC in cooperation with AT&T (which at the time owned all of the Bell Companies) and Independent Telcos. This requirement insured that residential customers would be able to connect five 500-type telephone sets to one POTS line. Each 500-type set contained a C4A ringer with an equivalent REN equal to 1. The FCC definition of a 1 REN load specifies the magnitude at 7000 ohms at 20 Hz. TR-57 Issue 2 specifies a specific R-C combination that has a 7000 ohm magnitude of impedance at 20 Hz. A REN loading requirement of less than 5 could conceivably be specified given that the majority of the embedded telephone station sets probably have a REN of less than 1 (e.g., 0.6). The ability to ring a customer line with 5 telephone stations sets is probably still desirable, but the corresponding REN load could be decreased to something on the order of 3 REN. A preliminary investigation, however, seems to indicate that there are other industry documents (most notably FCC Part 68, Section 3121, and TIA/EIA-470-B) that allow telephone terminal equipment to have a REN of 1. This suggests that any change in GR-57-CORE REN load requirements would need to occur in conjunction with these other industry groups (i.e., the TIA and ATIS). PROPOSAL BENEFIT(S): Cost reductions in network equipment could be obtained if a smaller capacitive load could to be support per analog line. The current proposal, however, is to take no action at this time to reduce the GR-57 specified 5 REN load because of the need to coordinate such an effort with other industry groups. A.2.2 BRIEF: Rational for Ring Trip Immunity Network What is the logic in selecting this current pre-trip test load? 8uF in parallel with 10K is an extreme test condition when compared to the actual application. This may limit the use of more creative and less costly ring trip schemes. DESCRIPTION: Requirement (R-11) in GR-57-CORE Section 5.4.5, Ring Trip Immunity, states: (R-11) A RT line unit shall not trip ringing when it applies an alerting signal to a termination of 10K ohms in parallel with 8 μF applied tip-to-ring directly at the output of the RT unit. PROPOSAL(S): As best as can be determined, this network was developed as follows: A 5 REN load, if purely capacitive, would be about 6 μF. A very long and very leaky loop could add an additional 2 μF. DLC systems are required to recognize 10 kilohms or greater as on-hook. Note that GR-909-CORE has a ring-trip immunity network of 10 kilohms in parallel with 6 μF. This would probably need to be made consistent with any changes made to GR-57-CORE. Given the above explanation the following new Ring Trip Immunity Network is proposed: (R-11) A RT line unit shall not trip ringing when it applies an alerting signal to a termination of 5 REN in parallel with 10K ohms and in parallel with 2.0 μF applied tip-to-ring directly at the output of the RT unit. Page 5 Telecommunications Industry Association TR41.1.1-06-02-006 Where 5 REN is defined as 1386 ohms in series with a 40μF capacitor (in accordance with Section 5.4.8 (R-23)). 10k-ohms is specified for the same reason as in the existing immunity network (i.e., it’s the lower bound of an on-hook condition for DLCs). 2μF (with no series resistor) is really a worst case condition since loop capacitance is a distributed capacitance (i.e., you get a ~82 ohms resistance in series with the capacitance for every 1000 feet of 26 ga cable). Page 6