INSTRUCTIONS AND CIRCUIT DESCRIPTION LORAIN MODEL F4A AND 4871-307 TONE GENERATOR 1. RATINGS Input: 46-52 volt d-c; 0.1 ampere Output: 600 Hz modulated at 120 Hz; 100 milliwatts 2. DESCRIPTION These Tone Generators produce continuous tone, suitable for use as dial tone. When interrupted, their tone output is also suitable for use as busy or overflow signal. Two separate output circuits are furnished. One circuit has two 4 volt windings in series which can be connected to an Interrupter tone gate circuit. The output voltage of the other circuit is adjustable between 0.5 volt and 10.5 volts. Model F4A differs from the 4871-307 Tone Generator in that Model F4A is equipped with a cover. a. Mounting Overall dimensions of Model F4A Tone Generator are 5-1/2 inches by 3-15/32 inches by 1-23/32 inches. Overall dimensions of the 4871-307 Tone Generator are 5-1/4 inches by 3-5/16 inches by 1-5/8 inches. Each unit has a male plug and two ball studs at the rear of the assembly. To install the Tone Generator, line up the male plug and the two ball studs with their matching receptacles and plug unit in. b. Electrical Connections Each Tone Generator has an eight prong male plug. Electrical connections are made to a matching female plug with terminals 1 to 8. (1) Connect terminals 5, 6 and 7 to an Interrupter tone gate circuit if interrupted dial tone is desired. Voltage Terminal +4V 5 0 6 +/-4V 7 2. b. (2) Adjustable tone output is available at terminals 3 and 4. Tone output voltage can be adjusted by connection of adjustment leads to two of Tone Generator output terminals 6 through 10 on trans­former T1, as follows: Tone Level T1 Transformer Voltage Terminals 0.5 . . . . . . . . . . . . . .6, 7 1.0 . . . . . . . . . . . . . .7, 8 1.5 . . . . . . . . . . . . . .6, 8 3.0 . . . . . . . . . . . . . .8, 9 4.0 . . . . . . . . . . . . . .7, 9 4.5 . . . . . . . . . . . . . .6, 9 6.0 . . . . . . . . . . . . . .9, 10 9.0 . . . . . . . . . . . . . .8, 10 10.0 . . . . . . . . . . . . . .7, 10 10.5 . . . . . . . . . . . . . .6, 10 (3 ) Supply nominal 48 volt negative battery, at terminal 1 and positive ground at terminal 2. CAUTION: Input battery polarity is critical. This Tone Generator will not operate unless input polarity is correct. 3. CIRCUIT DESCRIPTION a. Input Circuit DC input is supplied across series resistors R2 and R9. Voltage developed across R2 is furnished to pulse generator and amplifier circuits, which are described below. Capacitor C2 bypasses voltage transients, which would otherwise appear across resistor R2, to prevent transmission of noise to d-c output. b. Pulse Generator Transistor Q1, capacitor C1, resistors R7, R8, and R4, and potentiometer R3, make up a pulse generator. Initially, transistor Q1 is at cutoff. When d-c input is applied, capacitor C1 charges through resistances R3, R8, R7, and R9. Capacitor charge current flows until C1-R7 voltage increases to threshold emitter-base one voltage of Q1, at which time C1 discharges through Ql emitter to base one, and R7, When capacitor Cl completes discharge, Q1 emitter current ceases to flow and Q1 returns to cutoff. Capacitor C1 then recharges to repeat this cycle. Discharge interval of capacitor Cl is brief, so that transistor Ql conducts only for a brief interval during each pulse generator cycle. When Ql conducts, a current transient flows from positive input through resistor R4, base two to base one of Ql, and resistor R9 to negative input. This current causes a voltage transient (pulse) to be developed across resistor R4; voltage transients developed across R4 are supplied as pulse output. Setting of potentiometer R3 determines time-constant required to charge capacitor Cl, hence, it determines pulse repetition rate. Potentiometer R3 is adjusted to obtain a pulse repetition rate of 120 pps (pulse per second). c. Amplifier Each time a voltage transient appears across resitor R4, it causes a current transient to flow from positive input through resistor R5, emitter to base of transistor Q2, base two to base one of transistor Ql, and resistor R9 to negative input. This current transient momentarily drives Q2 to conduction. Transistor Q2 is connected in cascade with transistor Q3 to form a two­stage amplifier: when Q2 conducts, a current transient flows from positive input through Q3 emitter to base, ccapacitor C3, Q2 emitter to collector, and resistors R6 and R9, to negative input. This current momentarily drives Q3 to conduction. Base current of transistor Q3 charges capacitor C3. After each pulse interval, when Q3 base current ceases to flow, C3 voltage is applied across resistors R5 and Rl. Resistor Rl voltage is applied as positive base-emitter potential to Q3, to maintain Q3 at cutoff until pulse generator output again drives Q2 and Q3 to conduction. d. Output Circuit When transistor Q3 conducts, a current transient flows from positive input through Q3 emitter to collector, primary turns between terminals 2 to 3 of output transformer Tl, and resistor R9, to negative input. This current transient excites a tuned circuit, composed of transformer Tl primary winding and capacitor C4, to resonance at a frequency of 600 Hz. Since transistor Q3 supplies 120 current transients per second to transformer Tl and capacitor C3, Tl and C4 produce a 600 Hz damped wave which recurs 120 times per second. Primary winding current induces tone voltage in two tapped Tl secondary windings. One of the windings supplies two 4 volt outputs which can be connected to an Interrupter tone gate circuit. The other winding is tapped to provide adjustable tone voltage between 0.5 and 10.5 volts to other tone circuits. Either or both of these windings can be connected to supply tone current. Capacitor C4 is connected between TI primary terminal 1 or 2 and Tl primary terminal 4 or 5 as necessary to adjust resonant frequency of Tl and C4 to 600 Hz. LORAIN PRODUCTS CORPORATION Lorain, Ohio, U. S. A. LORAIN PRODUCTS (CANADA) LTD. St. Thomas, Ontario, Canada March 17, 1970 Form 1864 Printed in U. S. A.