ZETRON 748, Technical Manual

Page: 43 / 259

025-9368H 29
III OPERATION
The Model 748 Repeater Manager / Teleconnect does just as its name describes. It is an integrated
full-featured repeater panel with a full-featured radio-telephone interconnect. It is designed for
installation on full-duplex control stations or repeaters and to be used with half and full duplex
mobile radios. The Selcall version adds the functions of both a dial access paging terminal and a
mobile-to-mobile paging encoder, allowing a mix of equipment types in one system. The Roamer
version increases the ANI database size from 99 to 750 plus adds Wild ANI capability to the Selcall
version.
Half-duplex and full-duplex radio systems have different transmit and receive frequencies. A full-
duplex system allows the mobile to transmit and receive at the same time using two antennas or a
duplexer in the mobile and in the repeater. A half-duplex system is similar but half-duplex mobiles
don't have duplexers, nor do they have the ability to receive and transmit at the same time. This is
because in half-duplex mobiles, the receiver and transmitter both share common circuitry in an effort
to reduce the cost of the radios. Typical use for half-duplex would be mobiles and/or bases talking
through a repeater.
The Model 748 provides complete audio path control between the PSTN or a PBX and the control
station or repeater. It also provides repeat audio for tone/code validated repeater (dispatch)
operation. In addition, the unit can be programmed to provide repeat audio in handling no-tone
dispatch or require ANI validation (with or without tone/code validation) to access dispatch
operations.
For interconnect operation, each radio (user) may be specified as either a full or half duplex radio.
When operating full-duplex, the audio from the phone line is always output to the transmitter. When
operating half-duplex with repeat audio enabled, the radio's audio is repeated whenever the radio is
transmitting. If privacy is enabled, a masking tone is transmitted when the radio is transmitting.
This section describes the functional operation of the Model 748. A description of the interconnect
features and functions is first, followed by the repeater panel features and functions. Programming is
handled in Section 4.
INTERCONNECT OVERVIEW
The Model 748 Repeater Manager / Teleconnect is a multiple user, radio-telephone interconnect.
Radios or mobiles can place and receive telephone (PSTN or PBX) calls through the Model 748.
These types of calls are “Phone-to-Mobile” and “Mobile-to-Phone” calls. Radios or mobiles can also
place and receive calls to other radios or mobiles through the Model 748. These types of calls are
“Mobile-to-Mobile” calls. Radios or mobiles can gain validated repeater access through the Model
748 by using DTMF access codes. These types of calls are “ANI Mobile Repeat”. To accomplish
this requires that the Model 748 have some way of identifying each radio or mobile wishing to place
or receive calls through it. The Model 748 has two ways of doing this, User number or ANI
(Automatic Number Identification).