Ramsey Electronics SP1 User manual

HANDS-FREE
SPEAKERPHONE-
INTERCOM KIT
Ramsey Electronics Model No. SP1
How many times have you played acrobat juggling the phone
on your shoulder while looking up something or while working at
the bench? And, wouldn’t it be nice to be able to answer a call
from anywhere in your shop or garage? This handy
Speakerphone will do the trick and doubles as a hands-free
intercom too!
• Completely Hands-free; talk and listen at will
• Needs no battery - runs off the phone line
• Sensitive pick up throughout the room
• Excellent speaker volume
• Doubles as a hands-free intercom too! Connect as many units as
desired across 2 conductor wire
• Informative manual answers questions on theory, hook-ups and
uses - enhances resale value too!
• Includes our case for a finished ‘Pro’ look.
• Clear, concise assembly instructions carefully guide you to a
finished kit that works FIRST time!

SP-1 •2
PARTIAL LIST OF AVAILABLE KITS
RAMSEY TRANSMITTER KITS
• FM25B FM Stereo Transmitter
• AM1 AM Transmitter
• TV6 Television Transmitter
• FM100B Professional FM Stereo Transmitter
• STC1 Stereo Transmitter Companion
RAMSEY RECEIVER KITS
• FR1 FM Broadcast Receiver
• AR1 Aircraft Band Receiver
• SR2 Shortwave Receiver
• AA7 Active Antenna
• SC1 Shortwave Converter
RAMSEY HOBBY KITS
• SG7 Personal Speed Radar
• SS70A Speech Scrambler
• MX5, MX-10 Mixers
• MD3 Microwave Motion Detector
• ECG1 Heart Monitor
• LABC1 Lead Acid Battery Charger
• PG13 Plasma Generator
• SHA1 Stereo Headphone Amplifier
RAMSEY AMATEUR RADIO KITS
• DDF1 Doppler Direction Finder
• HR Series HF All Mode Receivers
• QRP Series HF CW Transmitters
• VLF1 Low Frequency SWL Converter
• CPO3 Code Practice Oscillator
• QRP Power Amplifiers
RAMSEY MINI-KITS
Many other kits are available for hobby, school, scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.
SP1 SPEAKERPHONE KIT INSTRUCTION MANUAL
Ramsey Electronics publication No. SP1 Revision E
First printing: January 1995
COPYRIGHT 1994 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York
14564. All rights reserved. No portion of this publication may be copied or duplicated without the
written permission of Ramsey Electronics, Inc. Printed in the United States of America.

SP-1 •3
SP1 HANDS-FREE
SPEAKERPHONE-
INTERCOM KIT
Ramsey Publication No. SP1
Price $5.00
TABLE OF CONTENTS
Introduction to the SP1...................4
Parts list for the SP1 ......................5
Parts layout diagram ......................6
Assembly instructions.....................7
Schematic diagram.......................12
Initial testing..................................15
Optimizing your set-up .................16
Understanding Speakerphones....17
Optional battery operation............18
Intercom operation .......................21
Warranty.......................................23
KITASSEMBLY
AND INSTRUCTION MANUAL FOR

SP-1 •4
INTRODUCTION TO THE RAMSEY SP1 SPEAKERPHONE:
There are, of course, all kinds of telephone accessories. Also just as various
"telephone amplifier" schemes have been around for years, the name
"speakerphone" is now a generic part of today's telephone vocabulary,
referring to hands-off talk-and-listen communicating. If we look at catalogs or
in phone stores, we also see that true hands-free speakerphones command
a handsome price or else may be designed only as accessories requiring
connection with a separate telephone.
The Ramsey SP1 Speakerphone gives you full, state-of-the-art
speakerphone technology...with a difference. First, it is a complete stand-
alone telephone for incoming calls. Use some other phone or dialer right
along with it only if you have a frequent need to initiate those unique
speakerphone-style calls. Otherwise, you can use your SP1 to answer all
incoming calls, handling them while you work or play. The SP1 is designed to
be practical and understandable, fun to build and to customize for your own
needs and decor.
The Ramsey Speakerphone is designed to let you stay in charge of your
time...on a budget. Think about the difference between that call you wish or
plan to place...and all those other calls that you ANSWER, whether you
wanted or expected them or not.
A pair of SP1's also makes a great hands-free INTERCOM system for which
you’ll imagine dozens of practical applications. You’ll figure out how to set
them up so they can serve as intercoms AND convenient speakerphones.
The kit style of the Ramsey SP1 lets you choose the type of enclosure and
the size of speaker for this very personalized call-answering or intercom
system. You will build a quality system around a high-tech Motorola IC, and
you'll never have to discard a plastic mystery box that has quit working for
you. The Ramsey SP1 Speakerphone PC board and circuit design are solid,
rugged applications of today's IC-based telephoning technology.
You may wish to read ahead and learn how to use the SP1 and how it works
before beginning actual kit construction. Build and learn about the Ramsey
SP1, and no other electronic telephone will ever again seem so intimidating
or mysterious!

SP-1 •5
PARTS SUPPLIED WITH SP1 KIT
CAPACITORS

1 100 pF disc [marked 100 or 101] (C1)
 4 .01 uF disc [marked .01, 103 or 10nf ] (C9,10,13,14)
 2 .05 or .047 uF disc [marked .047 or 473 or .05 or 503] (C3, C18)
 1 .1 uF disc [marked .1 or 104] (C28)
 8 .47 uF electrolytic (C2,C4,C6,C7,C8,C17,C22,C23)
 7 2.2 uF electrolytic (C5,C11,C15,C19,C20,C21,C29)
 2 47 uF electrolytic (C16,C26)
 1 220 uF electrolytic (C24)
 3 470 uF or 330 uF electrolytic (C12,C25,C27)
RESISTORS
 1 100 ohm [brown-black-brown] (R10)
 2 270 ohm [red-violet-brown] (R4 alternate R10)
 1 820 ohm [gray-red-brown] (R8)
 1 1K ohm [brown-black-red] (R2)
 4 4.7K ohm [yellow-violet-red] (R3,R9,R13,R19)
 4 10K ohm [brown-black-orange] (R1,R6,R14,R20)
 2 47K ohm [yellow-violet-orange] (R7,R12)
 4 100K ohm [brown-black-yellow] (R11,R15,R16,R17)
 1 68K ohm [blue-gray-orange] (R5)
SEMICONDUCTORS
 1 MC65118 28-pin DIP speakerphone IC (U1)
 1 LM386 8-pin DIP audio amplifier IC (U2)
 1 6.2 volt zener diode [gray body with black band] (D5)
 6 1N4002 black epoxy rectifier diode (D1,D2,D3,D4,D6,D7)
OTHER COMPONENTS
 1 miniature microphone element (MK1)
 2 1000-to-8 ohm audio transformer (T1,T2)
 1 2K,5K or 10K potentiometer (R18)
 2 PC mount DPDT push-switch (S1,S2)
HARDWARE AND MISC.
 1 SP1 printed circuit board
 1 28-pin DIP socket for U1
 1 subminiature phone/speaker jack (J1)
 1 modular telephone line jack (J2)
 1 9 volt battery snap connector (battery use is optional)
 1 5" hookup wire (optional connection "X" to "X")
REQUIRED, NOT SUPPLIED
 1 Modular telephone cord (your choice of length)
 1 8-ohm speaker
OPTIONAL: Ramsey CSP1 case and knob kit

SP-1 •6
SP-1 PARTS LAYOUT DIAGRAM

SP-1 •7
KIT BUILDING TIPS:
Use a good soldering technique - let your soldering iron tip gently heat the
traces to which you are soldering, heating both wires and pads simultaneously.
Apply the solder on the iron and the pad when the pad is hot enough to melt the
solder. The finished joint should look like a drop of water on paper, somewhat
soaked in.
Mount all electrical parts on the top side of the board provided, unless
otherwise specified. This is the side that has no traces or pads on it.
Electrical part installation - when parts are installed, the part is placed flat to the
board, and the leads are bent on the backside of the board to prevent the part
from falling out before soldering. The part is then soldered securely to the
board, and the remaining lead length is clipped off.
SP1 ASSEMBLY INSTRUCTIONS:
We have a twofold "strategy" for the order of the following kit assembly
steps. First, we install parts in physical relationship to each other, so there's
minimal chance of inserting wires into wrong holes. Second, whenever
possible, we install in an order that fits our "Learn As You Build" Kit-building
philosophy.
FOR EACH PART OUR WORD "INSTALL" ALWAYS MEANS THESE STEPS:
1. Pick the correct part value to start with.
2. Insert it into the correct PC board location.
3. Orient it correctly, which means: Please follow the PC board and
the written directions for all parts where there's a right way and a
wrong way to solder it in. (Diode bands, electrolytic capacitor
polarity, transistor shapes, dotted or notched ends of IC's, and so
forth).

SP-1 •8
4. Solder all connections unless directed otherwise. Use enough
heat and solder flow for clean, shiny, completed connections.
Don't be afraid of any pen-style soldering iron having enough heat
to damage components.
5. Trim or "nip" excess wire lengths after soldering.
 1. Install S1, the on-off switch, simply press it into position and solder all
six points. This switch is the equivalent of the telephone "hook"or handset
button. Incoming calls are answered by pressing S1.
 2. Similarly, install S2, the Mute switch. This switch can turn off the
microphone circuit without breaking the phone connection, providing a
privacy or "hold" function.
 3. Install R18, the volume control. It may have three of five soldering
points, with the optional outer two tabs offering additional mechanical
rigidity. Solder all points.
 4. Examine J2, the modular telephone jack. Press its pins into their
correct PC board location. Notice that the outer support posts are plastic
and are not to be soldered. If you anticipate heavy use of this jack
(frequent cord changing, moving, etc.) use a dab of glue to secure J2
before soldering. Solder all 4 connections for modular jack J2. If you look
closely, you'll see that only two pins are actually used in the circuit.
 5. Examine the subminiature jack (J1) supplied for speaker connection. It
fits into the PC board position easily. Notice that the tab nearest to the
edge of the board is connected to the common ground of the circuit. The
other two tabs are connected together to the SP1's speaker audio output.
You have a choice of installing J1 supplied or your own speaker wire,
depending on your intended application. Install J1 or a suitable length of
your own speaker wire.
 6. Examine the audio transformers, T1 and T2. Notice the red marking on
one side of the top insulator on each unit. These marked sides must be
pointed toward the center of the board, as shown by the dark sides for T1
and T2 on the PC board drawing. For each transformer (they are identical
units), a total of six solder connections should be made. The outer 2 tabs
are soldered to common ground for mechanical rigidity. Install
transformers T1 and T2.
Completion of your SP1 requires installing over 20 "jumper wires," designed
JMP1, JMP2, etc. These simple wire bridges are formed from scrap bare wire
snipped from resistors, capacitors or diodes. Unless you have a handy supply
of bare, tinned wire, be sure to save all cuttings for these jumper wires.
Jumper wires allow a single-sided PC board to have the benefits of a double-
sided PC board without the extra cost.
 7. A choice to make:

SP-1 •9
 A) If you plan to use your SP1 as a telephone speakerphone, install zener
diode D5 (small gray body with black band). The banded end marks the
cathode and must be oriented as illustrated.
 B) If you plan to use your SP1 only as a duplex intercom, do not install D5.
Place it in a safe place for possible future use.
 8. The six 1N4002 style black epoxy diodes are installed in upright or
vertical position. Correct orientation of the banded cathode ends is
important, so always install the diode body in the hole marked by the circle
on the PC board illustration. The banded or cathode end should face up.
The diodes may come with straight leads or pre-bent, ready-to-insert leads.
Install diode D1.
 9. Install D2, another black epoxy diode.
 10. Install D3, another black epoxy diode.
 11. Install D4, another black epoxy diode.
 12. Install D6, another black epoxy diode.
 13. Install D7, the last black epoxy diode.
 14a. The method for installing the microphone to face the
front panel and therefore requires soldering the MK1
element's terminals to three short bare wires (nipped from a
previously installed component), so that the three wires are
at right angles to the MK1 lugs. Notice that one MK1 lug is
common to its metal case and must be oriented toward the side of the
board so that it is connected to the common ground plane. You may wish to
do both ends of this connection first to hold MK1 in place to do the other
connections.
 14b. If the mike element has only two pins, install a bare wire jumper from
"D" to "E" and omit C5 (Step 16). Study the schematic diagram for any
clarification needed.
 14c. Install mike element MK1.
 14d. Solder a wire loop to secure the mike, using the 2 PC board holes on
each side of the microphone.
 15. Near MK1, install C9, .01 uF (marked .01 or 103 or 10 nf).
 16. Install C5, a 2.2 uF electrolytic. This is the first of 21 electrolytic used
in your SP1. Be sure to orient the (+) side as shown on the PC board
drawing. Note on electrolytic capacitors: Ordinarily, the negative (-) side is
clearly marked by a heavy stripe and the "-" sign. However, the positive (+)
side may be marked instead, especially on low values such as the eight .47

SP-1 •10
uF units used in this circuit. Simply make sure that correct polarity is
followed for all electrolytic capacitors.
 17. Install C7, a .47 uF electrolytic.
 18. Near the volume control, install R19, 4.7K (yellow-violet-red).
 19. Install R1, 10K (brown-black-orange).
 20. Near S1, install electrolytic C26, 47 uF.
 21. Install R16, 100K (brown-black-yellow)
 22. Install R3, 4.7K (yellow-violet-red).
At this point, we will begin installing jumper wires near parts already installed, if
you run short of useful wire lengths during assembly, simply skip that jumper
step and go back to it after you've built up your scrap wire supply. Jumpers act
as electronic "bridges" carrying signals over PC board traces underneath.
 23. Near R3, install JMP11.
 24. Install JMP5.
 25. Install JMP7 (between R16 and S2).
 26. Install C2, .47 uF electrolytic. Watch polarity.
 27. Install C3, .05 or .047 uF (marked .047 or 473 or .05 or 503).
 28. Install JMP6.
 29. Install JMP12.
 30. Install C13, .01 uF (marked .01 or 103).
 31. Install R8, 820 ohms (gray-red-brown).
 32. Install R4, 270 ohms (red-violet-brown).
 33. Install R12, 47K (yellow-violet-orange).
 34. Install C14, .01 uF (marked .01 or 103 or 10 nf).
 35. Install JMP15 (near T1).
 36. Install JMP18.
 37. Install C10, .01 uF (marked .01 or 10 nf or 103).
 38. Install R2, 1K (brown-black-red). Install the following jumpers.
 39. JMP14.