The CES Simplex Autopatch

Gregs Basic Electronics

Introduction To Basic Electronics

Get Instant Access

— some hot new hardware for two

One of the most controversial devices in a well-equipped repeater ts its autopatch. Some hams use autopatch facilities frequently, as part of their daily life, while others are very uncomfortable with autopatch usage for routine communications. Many re peater groups permit their autopatch to be used only for emergency calls or set strict time limits for routine calls. Whatever your views on autopatching are, you have to admit that in congested areas where repeaters receive heavy use, autopatching can create prob lems. Users trying to carry on a conversation grow tired of being interrupted by people needing the patch, and many a stranded motorist has increased his blood pressure to dangerous levels while trying to break into a long-winded monologue to call for help.

Communications Electronics Specialties, Inc., best known in amateur circles for their microphone-mounted tone pads and au-todialers, has come up with a fascinating solution to the autopatch problem, the CES 500SA. The 500SA is a simplex autopatch unit which interfaces an amateur transceiver to a standard phone line, No cavities or other hardware are required. You access the patch just as you would ac* cess the patch on a repeater: brings the patch up and "#" disconnects it from the phone line Now if you think about this for a moment, you might get a little confused How in the world can you operate an autopatch on a single frequency? It's not as difficult as it first seems.

How Jt Works

When the autopatch is not in use, it sits there waiting, patiently listening in the receive mode. When it receives a it connects the patch to the phone line and switches the transceiv-

Autopatch Diagram

CES Model 500SA simplex autopatch, er over to transmit. You hear a dial tone just as you would with a normal autopatch, with one important difference. Once per second, the patch samples its receiver for a "window" of anything from 5 to100 milliseconds, depending on the squefch characteristics of the receiver If there is a carrier present during this sampling window, the logic locks the system in the receive mode and doesn't switch back to transmit until the carrier drops. This ensures that the party on the other end or the phone line can t capture the transmitter.

It doesn't take much of an imagination to conclude that the constant switching between ¡receive and transmit will be audible, and indeed it is. How audible it is depends on how long ft takes the autopatch's transceiver to switch from transmit to receive and back again, and how good the squelch is on the transceiver you use to access the patch. CES provides information on how to modify your own transceiver to work with the patch, or they will sell you a Clegg FM-88 synthesized two-meter transceiver that is already modified. The most important change required for a transceiver to work with the 500SA is a simple mod that allows the receiver to stay on all the time- Using the modified Clegg FM-88 on the patch end and a standard Kenwood TR-7600 in the car, we found that the sampling window is audible, but never interferes with intelligibility. The sampling window makes the 500SA sound different than repeater autopatches, but in practice it works just as well.

tn the past, some hams have put together systems that used a VOXcircuit and stayed in the transmit mode whenever the person on the telephone was talking. When they stopped talking, the system switched back to receive, allowing the ham to talk. These systems were not legal. The person on the other end of the phone line was clearly in control of the transmitter, and if that person chose to talk about things that made you uncomfortable, you and every other ham on frequency had no choice but to listen. With the CES system, the ham is in control of the autopatch transmitter, because he can cause the patch's transmitter to shut down whenever he chooses, in one second or less..

Advantages of Simplex Autopatch

The advantages of a simplex autopatch are pretty obvious, but they are worth mentioning anyway. First of all, the patch only occupies one frequency, rather than a pair. In our increasingly congested amateur allocations, this becomes an important consideration. The ability to use a normal synthesized transceiver with the patch is positively enticing. Since the costs involved are negligible compared to a complete repeater, an individual or small group could easily put such a system on the air, or a repeater group could move autopatching activities off the repeater and onto a simplex frequency, freeing the repeater for normal QSOs.

A simplex autopatch could be extremely useful in an emergency situation when telephone communications fail, fust plug the 500SA into the phone system outside of the affected area, and police, fire, and medical teams can be given access to the phone system.

As it is presently configured, the 50GSA cannot be accessed through a repeater, but the manufacturer is developing some modifications to allow that use.

Many repeaters are located in remote areas where it \s impossible to bring in a phone line, and the 500SA could provide autopatch facilities for these systems.

While the concept of a simplex autopatch is revolutionary, it is only fair to mention that a similar system is presented in Bill Pasternak's and Mike Morris's epic tome, The Practical Handbook of FM and Repeaters, and has probably been discussed elsewhere as well. Simplex autopatches have been in use for several years, but the introduction of this commercially-built unit by CES will certainly increase the popularity of the simplex autopatch, With no further ado, let's take a good look at the 500SA,

Description

Physically speaking, there isn't much to the 500SA It is a well-finished metal box that measures 1-1 2 inches high by 9 inches deep by 10-1/2 inches wide. The front panel is a model of simplicity On the far right-hand side is a toggle switch marked "Toll Restrict," and it does just that. Inside the patch is a circuit board with 10 spaces available for the insertion of diodes. Our unit had diodes in the "0" and slots. Numbers starting with a 0 or 1 are consequently ignored by the decoder when the Toll Restrict switch is on.

Next to the Toll Restrict switch is a two-position rotary switch marked "Base" and "Patch". This allows you to completely bypass the patch electronics and use the transceiver as a normal base station. Next to this switch are two momentary-contact push-buttons marked "Disconnect" and "Connect" for manual testing of the patch. The last item sharing the front panel is a row of LEDs, to keep you informed of the status of the system's various functions.

Inside, construction is uniformly excellent. The glass-epoxy circuit board, high-quality components, and careful layout all serve as reminders that CES produces a wide range of equipment for the commercial radio services.

Moving to the back of the patch, we find a neatly grommeted hole with telephone wire exiting it The wire is equipped with a standard modular phone p!ugr so interfacing the patch to the phone line is not traumatic. Also on the rear panel are two multi-pin connectors for interfacing the unit with transceiver and IDer.

Installation and Use

We used a modified Clegg FM-88 as the transceiver for the patch, and setting up the system couldn't be simpler. CES thoughtfully wired up all the necessary functions to the accessory socket of the Clegg and provided an interface cable as well. Installation consequently took less than five minutes and consisted of hooking up the transceiver to a 12 V dc power supply, an antenna. and the autopatch, and plugging the autopatch into a phone jack. Power is supplied to the patch through the interface cable from the transceiver. The patch can be configured to work with either pulse or touchtone1^ phone systems; touchtone is a far-off dream in our area, so we had the optional pulse dialer installed.

Operation of the simplex autopatch is even less challenging than its installation As with any phone interconnect system that is not full duplex, you have to remind people that if they tafk at the same time you're talking, you won't hear them. Because of the once-per-

ORBIT is the Official Journal for the Radio Amateur satellite corporation

(A MS AT), P.O. BOX 27, Washington, DC 20047. Please write for application.

For a FREE SAMPLE COPY please send $1 to cover First Class postage and handling to: Orbit, 221 Long Swamp Road, wolcott, CT 06716, second sampling of the patch's receiver, you also have to be careful not to cut off the first part of a transmission, particularly when dialing. If you have a fancy tone pad or autodialer with automatic push-to-tafk, you'll have to forego the pleasures of that particular feature. Good operating practice with a simplex autopatch requires the transmitter to be keyed a couple of seconds before the first tone is sent, to allow the patch's logic to lock mto the receive mode.

The 500SA is equipped with a trme-out timer that gives warning beeps after 80% of timeout. The timer can be programmed to reset with a carrier, a or no reset at all. Our unit was programmed to reset with a which seems a good compromise.

One feature of the 500SA

that you may not wish to use is its reverse autopatch capability. When someone calls the autopatch, it transmits a beep to let you know that a call is waiting, (f you wish to talk to the caller, you simply press the on your tone pad to connect the phone line to the patch Since this system does not allow a control operator to screen the cafl before the caller goes on the air, tt is doubtful that the reverse autopatch function is legal under present FCC rules and regulations If you choose not to use this feature, it is easily disabled.

Legal Considerations

Many people I have talked with about the simplex autopatch have questioned the system's legality. After several phone calls to the :Ct\ I came to the conclusion that within the following limitations, the 501 SA is legal Fo: any auto-

patch to be legal, simplex or otherwise, a control operator has to be present at a control point for the transmitter, This rather dashes any hopes of simply plugging the thing in at home and having your own private autopatch. A ham will either have to be present in the room with the patch, or you'll have to arrange a control link to turn the patch on and off that is independent of the input frequency of the patch. If you monitor the patch whenever it is up and can shut the thing down if a wild turkey brings up the system, youII be well on your way to being legal.

The other thing you'll need if you want to be legal is an IDer CES offers one as an option for the 500SA, and at about 50 dollars, it's well worth the investment. The reverse autopatch feature? As mentioned above, the legality of reverse autopatch is doubtful at best, so you might as well disable that feature right away.

Applications

So how is the average ham going to use the 500SA? Well, the possibilities are almost endless! You could just plug the thing in at a good site and hope that the FCC never catches you operating it without a control operator That's just asking for trouble, and besides, there are some far more intriguing possibilities that are still within the capabilities of an individual ham.

Install the 500SA at a good site, hook up a 220 or 430-MHz control receiver, and bnng in a phone line. Designate anybody you wish as a control operator, and leave the patch normally disabled. Whenever one of the control operators wants to use the patch, he or she can activate it via the control link and then use it normally. This has the ad vantage of giving instant accessibility, yet it stays well within the letter and intent of the law.

The only disadvantage is that you need to have a transmitter for 220 or 4.10 as well as two meters to use the patch, since control functions cannot be performed on two meters The obvious solution is to put both the patch and its control receiver on the same band, say 220 MHz. install a 220-MHz transceiver in your car or use a handheld, and the one rig can handle both control and operating functions. Diat in the control frequency, bring up the patch, and then flip to the patch's operating frequency to place your call.

This approach seems ideal for the individual or small group with a closed system in mind. If the group grows or decides to make its facility available on an open basis, the patch could be left on all the time, as long as a control operator is monitoring the frequency

Conclusions

However you use it, the CES 500SA is a versatile and innovative new product. The concept is a logical oneF and CES has produced an autopatch system that should give dependable, trouble-free operation at a fraction of the cost of a repeater and its associated autopatch equipment,

If you or your group has ever wanted to have an autopatch system, as a convenience or for emergency use, you owe it to yourself to check out the CES 500SA!

For further information, contact Communications Electronics Specialties, inc., 260 W. New England Avenue. Winter Park FL 32789. Reader Service number 478. ■

Temperature Toi, - 4QDF 1o 150e F

Oscillator (Less Crystal I Price

Oscillator Type

Oscillator Range

Catalog Number

Temperature Toi, - 4QDF 1o 150e F

Oscillator (Less Crystal I Price

Oscillator Type

Oscillator Range

Catalog Number

Was this article helpful?

0 0

Responses

  • barbara
    How to use ham autopatch?
    8 years ago
  • claudia
    Can autopatch be operated on 2 meter simplex radio?
    8 years ago

Post a comment