The Model 35A Microconnect is a
multi-featured, microprocessor-based telephone interconnect designed
for use with simplex, half-duplex and full-duplex radio networks. It
gives mobile radio users an exceptionally reliable and flexible
method of placing and receiving phone calls. System operators will
benefit from the Model 35A�s flexibility; its user-programmable
features make it a �customized� phone patch that adapts to any
system�s specific needs.
Programming is done quickly and easily from any DTMF telephone or
mobile radio. The Microconnect is designed for system operators who
want complete control over their telephone interconnect system. Call
lengths, access codes, and toll inhibits can all be tailored so
phone connections never violate system regulations. If desired, an
operator can allow trusted users to override calling restrictions
with �Privileged User� access codes.
Simplex operators will find that the Microconnect significantly
upgrades their system�s operation. While other telephone
interconnects are either VOX or sampling units, the Model 35A
incorporates both methods for optimal simplex applications.
Mobile Access Codes
A mobile user places a telephone call by keying up and entering the
proper DTMF mobile access code.These programmable codes can be up to
10 digits in length. �Normal User� access codes are subject to the
programmable calling limitations. System managers or other
privileged users may originate calls using special �Privileged User�
access codes. These codes override any call restrictions such as
Toll Inhibit or time limitations.
After entering an access code, a mobile releases the PTT button to
verify access to the Microconnect. A valid
code causes the Microconnect to access the phone line, and the
mobile will receive a dial tone. If the access code is invalid, it
will be ignored. The Model 35A can also be set up to only accept a
certain access code that is sent automatically from a microphone,
not entered manually.
In the �No-DTMF Mobile Mode�, the Microconnect, equipped with an
external tone decoder, will allow a mobile radio without a DTMF pad
to gain access to autodial 9 simply by keying up and generating a
To ensure that mobile users abide by the system operator�s
regulations, the Model 35A checks all outgoing calls for programmed
call restrictions. If a forbidden entry is made, the call is aborted
and the mobile hears an error tone. Toll Inhibit may be programmed
to reject phone numbers with certain first or second digits
(second-digit restrictions are useful for private branch exchange
Up to four digits may be specified as invalid for the first or
second digit. If desired, any combination of first and second digit
restriction may be programmed.
Toll Inhibit may also be programmed to disallow phone numbers
according to length (e.g.; seven-digit maximum for public telephone
systems, four-digit maximum for PBX). The Microconnect can also
disallow Normal User overdial (DTMF transmitted by a Normal User
once a call has already been placed). This ensures that a Normal
User cannot redial after receiving the �second� dial tone that
appears under certain circumstances.
Simplex Sampling and VOX
The Model 35A Microconnect offers superb simplex operation since it
uses a VOX detector as well as dial tone and conversation sampling.
The owner can set up the Model 35A so it will always operate with
VOX, but if the phone audio remains continuous for the
�Into-Sampling Time�, the Microconnect will revert into sampling.
All of the VOX and sampling features are user-programmable, so the
Microconnect will adapt to fit the specific needs of any simplex
Simplex Digital Voice Delay
During simplex operation, no syllables will be lost by the finite
response times of the system�s components. The digital voice delay
option will key up the base station as soon as it receives an audio
transmission, but it will delay the audio broadcast for up to 1.5
seconds to prevent the loss of the initial syllables.
Half-Duplex Privacy Mode
In the privacy mode, a mobile eavesdropping on a phone
conversation will not be able to hear the conversing mobile�s audio
transmissions. The Model 35A does this by not retransmitting the
mobile�s audio portion at the radio site, and by sending masking
tones during the mobile�s audio broadcast.
Telco Answer Modes
Phone-to-mobile callers may request access to a mobile by dialing
the telephone number of the Microconnect. A caller will hear a
programmed number of standard telephone rings. The processing of the
call will depend on the answer mode. In the �Answer/Ringout� Mode,
the Microconnect will answer a caller and send a programmed number
of ringouts to the radio system.
An answered call is one that has been connected; a ringout is the
simulated ringing heard by the mobiles (and callers) that indicates
the presence of an incoming telephone call.
To prevent unwanted callers from accessing the radio system, the
�Answer/Access/Ringout� Mode will request a Telco Access code before
ringouts are sent to the mobiles.
An invalid code will disconnect a caller. The �No Answer/Ringout�
Mode will send ringouts to the mobiles, but the caller will not be
answered until a mobile responds.
The Microconnect can also answer an incoming call and give immediate
access of the radio channel to the telephone caller.
Model 35A (left) is fully enclosed in a low-profile aluminum chassis
that can sit under a standard 2500 series telephone. Installation is
facilitated by a modular phone jack for telephone connections.
Connections to the radio are made to a removable screw terminal
strip; normal connections are PTT (push-to-talk), COR
(carrier-operated relay), transmitter audio, and receiver audio; all
adjustments are made on the rear panel.
The digital delay board (below), which enhances both simplex and
half-duplex operation, fits securely inside the unit. All ICs on the
board and in the Model 35A are socketed for easy replacement or
servicing. All Zetron circuitry is thoroughly tested and backed by a
full one-year warranty.
- For use with simplex,
half-duplex, and fullduplex radio networks
- Regenerated DTMF or pulse
- VOX & sampling combined for
optimal simplex operation
nonvolatile system parameters
- Programmable mobile and telco
- Programmable Toll Inhibit and
Call Time Limit
- �Privileged User� access codes
- Privacy Mode for half-duplex
- Adjustable hybrid balance
- Auxiliary control-relay
accessible from phone or mobile
- Digital Voice Delay option
improves simplex operation
- All programming by DTMF via
telephone or mobile
- One year parts and labor