Communications Electronics

Consumer Products Division

P.O. 8ox 1045 □ Ann Arbor, Michigan48106-1CM5U.S.A For orders call 313-973-0860 or FAX 313-971-6000

Photo C. View of the piggy-bach MOSTEK microprocessor with the touchtone decoder. "Tone Decoded" LED is in the foreground.

CES continued from p 14 to the phone line. A six-foot cable with a modular plug comes with the unit.

There are two circuits in this unit not found in many autopatches. One is a VOX circuit that detects when the person on the phone is talking. This varies the sample rate in simplex operation. A noise-operated squeich simplifies connection to the radio receiver No COR ¡npui is needed, just raw non-deemphasized audio straight from the discriminator. A provided CTCSS input can be used as a COR mpul though, if you'd rather connect it that way.

An audio AGC circuit equalizes the audio level between the phone line and the transmitter.

To minimize possible noise problems, digital and audio circuits are separated on the PC board One side is digital, the other, audio, with separate voltage regulators for each side.

The Manual

The present manual is basically well written. but fails short in a few areas. Some func-lion descriptions aren't detailed enough. For example, the manual doesn't explain about Ihe CTCSS control input being used as a COR input Neither does the manual explain why there are three different letter A s in the CW programming chart. There are other redundant letiers in the chart When I called CES (they have a toll free number1) I was told that those letters are for foreign language use. One letter A was supposed to have two dots above it. Another A should have been printed with a bar above it, and so on with the other extraneous fetters Also, repeater controller operation is barefy mentioned The folks at CES assured me that a new manual is being prepared, and should be out by the time this review appears in print.


You can program the Smart patch and set its levels onJy after the patch s fully connected to the transmitter receiver, and phone line with Atfiich the unit is to be used.

Programming both the jumpers and the onboard EEPROM memory was not difficult. Most but not ail, of the jumpers are the pin and jumper block type. JP1 was a little tricky to find—it turned out to be a wire soldered between two holes in the board.

The programming section of the manual appears a bit intimidating at first, out once you get started it's not bad at alt. There are plenty of examples to help you with the codes. Plus, all parameters have preprogrammed default values in case you miss something.

It's best to go ihrough the manual and write down all of the programming codes you'll use first so that they can be entered easily once you start. There are timers that limit the time an entry may take, so it's good to have them worked out on paper beforehand.

EEPROM programming can be done locally with the supplied DTMF decoder or remotely via phone line. I enjoyed this part! The patch beeps ever/ couple of keysirokes to let you know you're proceeding properly, li you make an erroneous entry, it sends you an understandable CW error message

Setting audio levefs properly is a little hard er The writer of the instruction manual assumes thai you have on hand an FM service monitor or the combination of a deviation monitor, an audio generator, and an oscilloscope. Although I have the equipment, I tried setting it up by ear. 1 had everything sounding pretty good, t thought, until I actually tried to make a phone patch call and I couldn't make it work. The phone Jine wouldn't accept the digits t was dialing, t had to use an oscilloscope to set the ievel from the receiver into the patch, and the audio ievel into the phone line.

It took me less than an hour to get operational the first time, and that includes wiring everything together!


I tested the patch in two different settings, First 1 tried it in simplex mode with my ICOM JC-245 synthesized two meter transceiver Then I tried it as a repeater controller and autopatch with a 220 MHz Motorola MtCOR based repeater in boih modes of operation, the pa:ch offers the standard timeout and activity timers, toll restrict, toll restrict override controls, and reverse patch operation

The connect and disconnect codes can either be the standard * up and tf down, or programmable three-digit codes.

Toll restrict can be programmed to work on either the first or second digit dialed. Both digits are programmable Toll restrict can be totally enabled or disabled, or you can enter a special override code which allows you to make one loll call After disconnect, it automatically rearms.

Simplex Operation

In simplex mode, the patch worked well wilh my synthesized ICOM ihe default sample window time of 60 ms was more than adequate. 1 was even able to reduce it to 25 ms with the rig in low power mode.

The constant "kerchunks" ! had 1o listen through when using the patch with a synthe sized rig bothered me, but this patch senses when the person on the phone is talking (the VOX circuit) and slows down the sample rate so that the kerchunks are not as frequent when you're trying to listen. The patch samples in between syilables rather than words, and the sample rate changes and slows down belween pauses. Dial tone and other telephone signals won't fool it, thanks to the call progress tone filter in the DTMF decoder.

If a crystal-controlled rig had been used with a shortened squelch time constant, the "kerchunk" would have been reduced to a less bothersome "click."

Repeater Operation

With the patch connected to my repeater, \ learned its repeater controller functions, There is a transmitter timeout timer and an ID interval timer that must be set. in addition to the autopatch timers. If the Auto ID mode is activated, the repeater call must be programmed tnto memory as well. A single, non-programmablet courtesy beep can be enabled or disabled It has an associated programmable "PTT Delay1' timer for keeping the transmitter up after the beep.

There is also an autopatch enable control that allows the controE operator to enable or disable the autopatch function without affecting its operation as a repeater controller,

The unit has two functions for turning on and off external devices, but strangely, they are not brought to the outside world. CES pians to include an addendum in future manuals that will show you how to access these functions.

Since I had the repeater connected to my home phone line while I tested the patch. I especially appreciated one feature of the patch—it won't allow an interconnect if the phone line is already busy. This is great when your repeater is located in your home and your wife is using the phone. She won't get a rude earful of touchtones from someone attempting to make an autopatch call, nor will her

CES 510SA-II Specifications

Modes of Operation ConnectyDisconnect Codes: Simplex Sample Window:

Simplex Sample Rate: Call Limit Timer: Activity Timer Rptr Timeout Timer: Rptr Hang Time; Timeout Warnings; Toll Restrict: Automatic Ring Out: Toll Restrict Defeat: Automatic CW ID: Dialing:

Phone Busy Lockout: Busy Chan. Xmit Lockout: User Control output: Remote Disable: CTCSS Enable ■ Disable:

Audio Requirements:



interface Signals Req'd:


Dimensions: Weight:

Power Requirements:

Simplex, half, or full duplex


2ms-512ms l00ms-3.000ms up to 42 minutes up to 4 minutes up to 16.6 minutes up to 9.99sec

10 seconds ot warning beeps 1 st or 2nd digit programmable General or Directed Three digit code Five programmable

DTMF or pulse. Europulse DTMF not regenerated

User selectable option

User selectable option

MOSFET drain pulling to ground

Rear connection

Rear connection

50~2000mV RMS 0-1 V RMS

Ground, -H2V, PTT.Tx audio rcvr discriminator audio Telephone tip  ring

Locally via supplied DTMF keypad, or remotely via phone line

10-15 VDC at 300mA

Table 1

Full-duplex, Half-duplex, Simplex?

These terms refer to the way the epeater or autopatch handles audio information. Full-duplex means that audio passes into and out of the phone patch at the same time. A normal land-line telephone operates full-duplex because one can talk and listen simultaneously. A repeater is a full-duplex system because it receives and transmits simultaneously A full-duplex autopatch allows you to taik and listen simultaneously.

Half-duplex means that information fiows in only one direction at a time, even if the transmit path is on a different frequency from Ihe receive path. Most radio transceivers are half-duplex devices. Vou can either transmit or receive, but not both simultaneously. Most autopatch systems operate in half-duplex mode not because the repeater and autopatches can t receive and transmit simultaneously, but because the users can't.

Simplex operation refers to the fact that both transmitting and receiving take place on the same frequency, but not simultaneously. You need only a transceiver for this, not a repeater A simplex autopatch.

after activation, transmits the audio coming from the phone line. Every second or so, the simplex autopatch switches the transceiver from transmit to receive for a very brief time, typically 25-75 milliseconds. If a signal is received during this "sample window", the autopatch win hold the transceiver in receive mode until the signal ends, at which time the transceiver wilt be swiiched back to transmit mode.

A station listening to a simplex autopatch will hear the person on the phone line interrupted by a "click" every second or so. That's the sample window. To capture the receiver, the transmitting station must hold his transmitter on until a sampling occurs. Then he can talk to the person on the phone. Though it doesn't have the interactivity of a normal phone conversation, and has the annoying sampling interrupts, it gets the job done using only one frequency, and doesn't require a repeater. Anyone who has a transceiver can have his own autopatch. Be sure to check out the FCC regulations pertaining to simplex operation before putting such a system on the air.

conversation suddenly end up on the air. This is a definite marriage saver! If you're not married or don't care, you can use the jumper provided to defeat this feature.

Reverse Patch

There are two modes of reverse patch operation The first is "Auto Answer" mode. In this mode, the patch will answer the phone after a preprogrammed number of rings and wait a preprogrammed time for further control codes.

The caller can then enter a remote programming codet or a multi-digit security code. If the correct security code is entered, the patch will immediately connect to the phone line. If neither the programming code nor the immediate connect security code is entered, or if the channel is not busy, the transmitter then regenerates part of the security code. A design nated mobile can then complete the connection by dialing in the same code that was transmitted to him.

in the Non-auto Answer" mode, the patch senses the phone ringing and generates a long beep out over the air. Anyone can then answer the phone by just dialing the regular connect code.

In either reverse patch moder the patch monitors the receiver and wili not allow itself to bring up the transmitter when it senses a signal already on frequency, (f a signal is on frequency, the person calling on the phone line hears an error message and the call is then terminated. Software allows you to defeat this feature.


This patch performs excellently. Its audio quality is excellent. Programming is flexible and is easily done remotely, I suggest below, however, a few improvements-

First, the instruction manual needs some elaboration in certain areas. Second, CES Should consider putting a decent connector on the rear of the unit, and labelling the connector terminals. The terminal block on this patch is on the circuit board inside the unit, requiring cover removal for wire connects/disconnects. You also have to refer to a diagram in the manual and then count positions to find the right terminal.

Third. CES shouid move to the front panef an LED on the PC board that indicates when a DTMF tone is decoded. In a DTMF-dependent device such as this a "tone decoded' indicator is as important to monitor as a noise or PTT indicator.

Fourth, there should be automatic stop-bit insertion. When J programmed in my call letters, I forgot to also program in a stop bit as mentioned in the manual. This caused several extraneous characters to be sent after my call Though easily corrected, there's no reason why internal software can t automatically insert the stop bit when one exits the programming mode, to completely avoid this snag

Fifth, though the unit contains the circuitry capable of doing this, it doesn't regenerate touchtones into the phone line. The patch stores the phone number and rediais it as pulses, but not as touchtones. A slight software change here can eliminate one of the bigger headaches in autopatchdom? In Sum

The above comments fall in the category of nilpicks The CES 510SA-II telephone interconnect is an excellent autopatch and repeater controller, from a company with an excellent reputation. Before doing this review, i had heard nothing but good reports from friends who own this model Now that I've had the chance to test one myself, I can say that if you're looking for a good mid-featured auto-patch/repeater controller, the Smartpatch II from CES is an excellent choice. (H

73 Book Review

Wishbook of Circuits

Circuits for QRP, signal generators, and much, much more.

reweivetf £>y Larry Antonuk WB9RRT

Master Guide to Electronic Circuits hy Harry Lt Helms Published by Premice-Hail Englewood Cliffs. NJ 07632 Hardbound. 293 pages, illustrated, 1988

The latest entry in the "circuit compilation/ wish hook" category comcs from Harry Helms. Master Guide to Electronic Circuits is a collection of electronic schematics, each backed up with a short paragraph of explanation, This type of book is quite useful for the person searching for a specific type of circuit. The original source is listed u ith each circuit, so the builder can go hack and find PC board layouts, pictorials, etc. The book also fits the casual reading category—nice for browsing through, for thinking that well, someday, Td sure like to build one of those.

¡'he circuits contained in the Master Guide are drawn from several sources. Most of the information comes from manufacturer's data sheets and application notes. Hams will like the fact that the remainder of the circuits come from 73, C0, Ham Radio, and QST. As a matter of fact, ihese are the only magazines that the author drew from. This makes for a pleasing absence of FlashingLED and Freezer-Failurc-Alarm circuiis.

In addition to the expected signal generators and QRP transmitters, though, we do have enough variety to make things interesting, The strong of heart can whip up their own Computer Modem or Bicycle Mileage Computer, Part-time medical doctors might want to build an Electrocardiograph Amplifier, or perhaps a Heart Rate Monitor. Or how about Automatic Cruise Control? You name it. it's probably in there.

The graphics in Master Guide to Electronic Circuits are quite good. E he preface lets us know that the schematics don't ail match one another because they are still in the style used by each publisher. While this comes across as a light apology, it's actually stating a strong point. Using material directly from the source eleminates another step in the process that could easily introduce errors.

Master Guide, being a good collection of the most current electronic circuits, is a source of inspiration. Used in conjunction with the originally published material, it will save the builder hours of research time, Q)

Ham Radio & Computer EXPO '88

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