Delta Electronics, Inc.

Model 6740B and Model 6742B
3-1/8" EIA Coaxial Transfer Switches

Model 6740B


The Model 6740B and Model 6742B Coaxial Transfer Switches are double-pole, double throw, high power switches for use with 3-1/8 inch 50 Ohm transmission line. The manually or remotely operated transfer switches enable the changing of coaxial connections between transmitters and antennas/dummy loads with a minimum of changeover or off-air-time. Transmission line switching occurs in less than two seconds. The Model 6740B operates with 120 VAC, 50/60 Hz main power and the Model 6742B operates with 220/240 VAC, 50/60 Hz main power.


Coaxial transfer switches are used to switch transmitters, transmission lines, antennas, dummy loads and auxiliary equipment quickly and efficiently when failures occur, when operating procedures are changed, or during scheduled maintenance periods. They also simplify equipment tuning, testing, and emergency repairs by facilitating quick checks under actual operating conditions.

Many switching requirements in a station are greatly reduced by the use of transfer switches. In complex systems, only one-third or one-fourth as many transfer switches are needed to accomplish the same switching function as a system using SPDT or SP3T type switches. If only three of the terminals in the Model 6740B or 6742B switch are employed, the switch can be used as a SPDT type.

The Models 6740B and 6742B can be pressurized up to 15 lb/sq in (1.1 kg/sq cm). A gas barrier is built into each terminal and an air inlet port is provided.

The Coaxial Transfer Switch provides two isolated interlock circuits for each switch connection that duplicate the RF path exactly. All interlock switches open before the RF contacts open, and close after the RF contacts close to prevent switching with RF power applied. Additional internal switch contacts enable remote control and status indication. All interlock, indicator and control circuits interface the transfer switch through a connector.

The transfer switch can be remotely controlled using either a high level, direct AC main power switching interface or a low level, open collector/contact closure interface. The Model 33630A Coaxial Switch Control Panel controls either a Model 6740B or Model 6742B Coaxial Transfer Switch and indicates the switch connections. The control panel operates with 120 VAC or 220/240 VAC, 50/60 Hz main power and mounts in a standard equipment rack space of 3-1/2" high by 19" wide.

Model 33630A
Model 33630A Coaxial Switch Control Panel

Optionally, the transfer switch can be supplied with internal relays to provide an open collector or contact closure interface for low level control applications. The low level control signal needs to be maintained only for the duration of the switching cycle. Low level interface relays for operation with either 12, 24 or 48 VDC control circuits are available. Consult the factory with your requirements.


Termination, Male EIA Flange: 3-1/8 in 3-1/8 in
Frequency Range, MHz:0-216†0-216†
Impedance, Ohms:5050
Average Power Rating*, kW:
 @ 50 MHz
 @ 108 MHz
 @ 216 MHz


Peak Power Rating*, kW:400400
VSWR, Guaranteed Maximum:1.041.04
Isolation, Typical, dB:6060
Insertion Loss, dB:0.10.1
Switching Time, Maximum, Seconds:22
PressurizationYes, 15 lbs/sq inYes, 15 lbs/sq in
Power Source:

120 VAC ±10%,
50/60 Hz
220/240 VAC ±5%,
50/60 Hz
Optional Interface Relay Operation Power, Nominal, Watts:11
Power Drain, Watts (during switching):200200
Interlock Contact Rating:
 @ 24 VDC/120 VAC

 @ 240 VAC

7 Amps Res,
5 Amps Ind
6 Amps Res,
4 Amps Ind

7 Amps Res,
5 Amps Ind
6 Amps Res,
4 Amps Ind
(L x W x D)
14 x 14 x 14
360 x 360 x 360
14 x 14 x 14
360 x 360 x 360
Order Numbers:
  Switch with 4 standard
   3-1/8" EIA connectors
  Model 33630A Coaxial
   Switch Control Panel

Low Level Interface Relays12 VDC24 VDC48 VDC
   Factory Modification Kit942-0092-001942-0092-002942-0092-003
   Field Modification Kit942-0103-001942-0103-002942-0103-003

*At unity VSWR and 40º C (104º F) ambient temperature.
Model 6740B/6742B switches may be used at frequencies above 216 MHz with derating of average power, VSWR, isolation and insertion loss specifications. Consult the factory with your requirements.

For additional information on any of our products, please contact Sales to discuss your particular requirements:
Delta Electronics, Inc.
5730 General Washington Drive
P. O. Box 11268
Alexandria, VA 22312
Phone: (703) 354-3350
U.S. Toll Free: 1-800-8-DELTA-8 (1-800-833-5828)
Fax: (703) 354-0216

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